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The name isssssssssss Viper! And I'm going to do a little experiment in the biology lab!
~ Dr. Viper

Dr. Viper is one of the principal antagonists in SWAT Kats: The Radical Squadron, particularly serving as the secondary antagonist. He appeared in five episodes total.

He was voiced by Frank Welker.


The Viper Mutagen

Dr. Viper used to be an unremarkable biochemist named Dr. Elrod Purvis, who worked at Megakat Biochemical Labs as an assistant to Dr. N. Zyme. After years of research, the two co-created Viper Mutagen 368. The noble Dr. Zyme planned to donate the formula to the city, but Purvis had other ideas.

Dr. Purvis covets the Viper Mutagen.

Deciding he wanted to get rich off of the formula, he decided to try to steal the Viper Mutagen, to sell to the highest bidder. Dr. Zyme, however, returned to the lab and caught him in the act. A fight broke out, which ended with Purvis taking a fall down a flight of stairs, spilling the chemical all over himself in the process and seeming to die.

Later, at the city morgue, the Viper Mutagen took effect, and resurrected Purvis - unfortunately, it had a disastrous side effect, causing Purvis to mutate into creature that is half cat, half snake, and with no soul.

Dr. Purvis revealing himself as "Dr. Viper".

After scaring a hapless attendant and causing him to go into shock, Purvis, now calling himself "Dr. Viper," proceeded back to Megakat Biochemical Labs, where he rounded up Mayor Manx and Deputy Mayor Briggs, who were visiting the lab, and Dr. Zyme as his prisoners, planning to mutate them all into cat/snake beings like himself with a new batch of Viper Mutagen. Luckily for them all, the SWAT Kats arrived in the nick of time and stopped the mad scientist and his army of mutant bugs. However, Dr. Viper escaped after being knocked out the window.

Since then, he has made Megakat Swamp his home, living in a lifeless area full of malformed giant trees known as "the Dead Forest," hatching many a scheme to transform the world into an environment only his depraved mind could love: a festering, mutation-filled wasteland.

Katalyst 99

His first scheme involved obtaining a rare compound called Katalyst 99 from his former place of employment. Another villain named Morbulus had recently been defeated by the SWAT Kats and escaped into a sewer drain pipe, where he met Viper. Viper took him back to his lair in the Dead Forest, where he turned him into a giant purple bacteria monster, intending to use him in his newly mutated form to break into Megakat Biochemical to steal the katalyst.

Viper explaining his plan to Morbulus.

During this particular caper, many innocent cats were killed by being eaten by Viper's bacteria monsters. They ate a subway train full of commuters and a farmer, and even Dr. Zyme is also thought to have been eaten by one of the creatures. Viper himself fed the farmer to the monster as punishment for trying to attack his creation with his pitchfork.

He'd thought ahead, making the monster immune to antibiotics and also giving it the ability to divide into more of itself when hit. He failed when the SWAT Kats killed them all by electrocuting them. Nevertheless, he did get inside the lab where he took Callie Briggs prisoner. The SWAT Kats almost took him into custody, but he blew up the lab using the (as it turned out) highly combustible katalysts. The SWAT Kats and Callie got out alive but Viper seemed to have died.

The Megakat Tower

But Viper was back again for a third attempt, this time setting his sights on the newly constructed office building dubbed the Megakat Tower. Its great height - 300 stories - meant it was perfect for his plan to place a mutant spore pod on the roof, which would explode and spread mutant plant spores all of the city, thereby turning it into the "Megaswamp City" of his dreams.

Viper showing Callie the spore pod.

Disguised as a gardener, Viper pretended to water the building's potted plants, but was in reality dousing them with his mutagenic growth formula, which turned them into monsters which he called Plantimals. He took Callie Briggs hostage and held her in the skyscraper's penthouse.

A thick wall of vines kept the Enforcers out, while flying Plantimals guarded the roof. Razor was able to infiltrate the building and come up on Viper from underneath however. During this time it was discovered extreme cold killed the monsters, so T-Bone, after rescuing Razor and Callie, dumped a tank of rocket coolant obtained from MASA onto the tower, freezing all of the plant monsters and seemingly Viper himself.

The Invincible Alliance of Evil

A thawed out Viper later returned his attention to Megakat Biochemical (since rebuilt) and its supply of katalysts. In particular, he wanted Katalyst 100. Joined by his latest creation, a huge, hungry half cat, half mushroom creature that served as his assistant, he broke in, with the mushroom monster eating the guards in the process. Viper was shocked and angered to discover Dark Kat's Creeplings already inside, in the process of stealing the katalyst.

Viper considers Dark Kat's offer.

A fight broke out between Viper and the Creeplings over possession of the flask, interrupted by the SWAT Kats. In the ensuing conflict, Megakat Biochemical was blown up again. All the Creeplings died and Viper's mushroom monster wound up splattered all over the Turbokat. Viper survived and confronted Dark Kat, who proposed an alliance. The two even forcibly recruited the Metallikats to their cause and Viper also reformed his mushroom monster (or made another). The group of five villains (including Viper's monster) made it their sole goal to kill the SWAT Kats and divide Megakat City equally among them.

Dark Kat betraying Viper.

After several failed attempts, the villains soon had T-Bone, Razor, Callie and Mayor Manx imprisoned inside a force field bubble in Dark Kat's hideout. Dark Kat revealed his intention to betray his allies and rule the city by himself, and so a fight broke out among the villains. Aside from knocking a Creepling into his mushroom monster's mouth, Viper mostly stayed on the sidelines. When Commander Feral freed the captives and the SWAT Kats successfully trapped Dark Kat, the Metallikats and the mushroom monster, Viper attempted to escape but was collared by Feral and then thrown into prison with the other villains.

Dark Kat then set off a bomb, declaring if he lost, everyone lost. The heroes made it out safely but all of the villains were inside when it blew up. Like his former allies, Viper was again thought dead.

"Mutation City"

But the sinister scientist survived to make one final try at conquering Megakat City. He stole a shipment of Katalyst X-63 and used it to flood the city, mutating numerous animals into giant monsters. He even poured some of it on himself and surfaced as a skyscraper-sized giant cat-snake monster with immense strength and the ability to shoot acid from his fingertips.

Viper as a giant monster.

The Enforcers' Dr. Konway deduced the antidote to X-63 was a supply of anti-mutagen chemicals found in Megakat Biochemical Labs, once more rebuilt. The SWAT Kats undertook a perilous mission through the mutant-infested city to get there. T-Bone, bitten by a mutant, turned into a half cat, half frog monster and had to be knocked out and restrained by his partner.

Razor then tried to fly the two huge tanks of anti-mutagens back to Enforcer Headquarters, but was intercepted by the giant Viper, who grabbed the tanks and held them aloft in victory, laughing insanely. Razor fire Match-Head Missiles into the tanks, and they exploded in Viper's face. The anti-mutagens, in a gaseous form, spread through the city, returning T-Bone and all the mutated animals to normal. Viper's fate following this is unknown.

The Unfinished Episode: The Doctors of Doom

Planned as the season two finale, The Doctors of Doom would've seen Viper teaming up with Dr. Harley Street, the MASA scientist bitten and converted into an autonomous Ci-Kat-A drone by the alien queen in The Ci-Kat-A. In this unfinished premise, which was apparently never fully scripted, Viper, following the events of Mutation City, would've been reverted to his previously mutated form after being gassed by the anti-mutagens, although he would've retained the ability to shoot acid from his fingertips.

The Doctors of Doom would've revealed that after Dr. Street fell from the Megakat Tower at the end of The Ci-Kat-A, he crawled into the sewer, Viper nursed him back to health under the agreement that Street would help him steal Super Katalyst S66 from Megakat Biochemical Labs so Viper could (he claimed) use it to help the Ci-Kat-A race take over the world, as this was Street's only driving goal.

After biting and converting a group of escaped prisoners who stumbled across Viper's swamp lair, Street and his new group of "brothers" successfully stole the katalyst, even gaining yet another follower when one of the converted prisoners bit Enforcer rookie Gray Taylor. Street, Taylor and the former prisoners returned to Viper's lab, where Viper betrayed them by putting them to sleep using knockout gas and then using the stolen S66 to mutate the already transformed group even further, turning Street into an enormous, armored black scarab, and Taylor and the prisoners into armored white grub creatures.

Viper's true plan all along was to use the katalyst to turn his erstwhile "allies" into mindlessly obedient monsters, just as he'd done with Morbulus. He accompanied the scarab and grubs to the Megakat Thermonuclear Plant with the intention of making its reactor go critical, in order to trigger a meltdown to destroy the entire city, so he could create a (now radioactive) mutant-infested swampland (which he now intended to call "Viper City" instead of Megaswamp City or Mutation City). However, he was stopped by the SWAT Kats, who killed his tragic, twice-mutated insect minions, while he himself escaped by swimming away into Megakat Bay.


Dr. Purvis was shown to be extremely manipulative, opportunistic, sarcastic, and greedy. When Dr. Zyme revealed he intended to donate the Viper Mutagen to the city, Purvis considered him an idealistic fool who was throwing money away. The scientific research Purvis conducted was not undertaken for the betterment of catkind; his end goal was solely to get wealthy.

Purvis punches Zyme.

He was also shown to be quite vicious if provoked and uncaring about whether anyone got hurt in his schemes - when Zyme tried to stop him from stealing the mutagen, Purvis punched him in the face and knocked him down a flight of stairs. His readiness to violate the rights of others in furtherance of his plans marks him as a sociopath.

As Dr. Viper, Purvis was no longer motivated by money, and his sociopathic tendencies were amplified a hundredfold. He was also incredibly argumentative, sadistic, cruel, callous, and abusive to others. He seemed to take sick pleasure in Morbulus' slow and painful transformation, and didn't care how many people died in all his attempts to conquer the city. Viper even seemed to delight in the thought of the citizens dying, and he referred to his monsters eating innocent victims in sarcastic food terms - "Now that you've had your breakast/Dinner" etc.

Viper's lair in the Dead Forest was indicative of what he considered beautiful.

Through his monsters, Viper is indirectly responsible for the deaths of at least twenty to thirty people throughout his various appearances, and directly responsible for one - when a farmer attempts to attack his bacteria monster, Viper is enraged and grabs the farmer with his tail and puts him into the monster's mouth to be eaten, directly murdering him.

Viper was also very insane and psychopathic, and his sense of aesthetics was warped and twisted. He considered his hideous monsters "beautiful" and considered modern architecture "ugly" and his single driving goal was to turn the modern metropolis into a festering mutation-filled swampland, over which he personally would rule. His home in the Dead Forest, a giant, twisted tree, is a good representation of his warped sense of taste.

Powers and Abilities

Viper was a highly skilled biochemist.

Purvis was implied to be a biochemist of mediocre ability and intelligence. Although he assisted in the Viper Mutagen's development, most of the formula's ingredients were Zyme's idea. Consequently, Purvis couldn't come up with an idea of his own to get rich, he could only steal the ideas of others. He was of average strength, although exactly how good of a fighter he was is difficult to gauge when the only time ever attacked someone was to knock the unprepared and middle-aged Dr. Zyme down the stairs.

Dr. Viper is a far more creative and intelligent scientist. Whatever he needs to do he can accomplish scientifically through judicious use of different chemicals. He also displays some ability in the area of robotics and mechanical science, since he was able to help Dark Kat build new bodies for the Metallikats (how much he contributed, though, isn't known).

Viper's eyes glowed in the dark.

In the field of biochemistry and mutation, Viper is able to take almost any living thing and turn it into a ravenous monster to suit his purposes. Through some unknown means, he also has total mastery over all of his monsters. Whether created directly, or mutated from something else, they all obey Viper without question. It is possible this is due to some unknown ingredient in the chemicals he employs, or simply through sheer force of will.

The physical abilities granted to him as a result of his mutation are many and varied. His eyes glow in the dark, and this could suggest he has the ability to see in dark places, although this is never outright stated.

Viper using his snakelike tail to grab people.

He has pure Viper Mutagen for blood. Consuming his blood will mutate whatever drinks it. Since the Viper Mutagen was intended to revitalize dead or dying cells it's also possible that the mutagen in his bloodstream is why Viper can recover so easily from explosions, freezing, long falls and other accidents that would kill normal cats - the mutagen revives him every single time.

His long, snakelike tail is his primary weapon. It can be swung and used to smash things or knock down opponents, and is also prehensile and can be used to grab people or objects. He also has sharp claws and fangs, although it is unknown if he has any venom.


Dr. Viper has created, directly or indirectly, a wide variety of monsters during his career as a mad scientist in Megakat City.

  • Killer Wasps: Dr. Viper's very first creations. Gigantic wasps which drank his Viper Mutagen-tainted blood. They had the ability to shoot their barbed stingers at enemies.
  • Mosquitoes: Another one of Viper's first creations. Giant mosquitoes, created in the same manner as the wasps. They spat a sparkling, pinkish-colored fluid onto their victims which caused temporary paralysis.
  • Bacteria Monster: An enormous, four-eyed purple germ monster created when Dr. Viper mutated Morbulus using his new bacteria strain. The creature(s) divided like amoebas whenever they were hit, and were insatiably ravenous. They were immune to antibiotics, and their only weakness was being electrocuted.
  • Plantimals: Half-animal, half-plant monsters which Dr. Viper used as his bodyguards when he took over the Megakat Tower. They were immune to weed killer, which only mutate them into a deadlier, larger form. Cold was their only weakness. They came in many different varieties, several of which spat corrosive acid:
    • Flyers: Winged, yellow Plantimals with red flips. They defended the spore pod in the penthouse. T-Bone nicknamed them "sap-slingers" due to their acid-spitting ability.
    • Rovers: The most common kind of Plantimal, which were greenish yellow and had purple lips. They ran around on two legs and were the only kind of Plantimal that didn't spit acid (although a scene in the script for Destructive Nature cut from the final episode revealed they have acidic blood).
    • Behemoths: The largest type of Plantimal, which had huge, fanged mouths and three nozzle-like tentacles on their backs which sprayed acid at enemies. One of these guarded the entrance to the Megakat Tower and was mutated when doused in weed killer.
  • Mushroom Monster: Viper's assistant, who was a tentacled, half-kat, half-mushroom creature, who was more intelligent than his other creations by far. Like most of Viper's monsters, he was ravenous and ate almost anything. Nicknamed "Fungusface" by Dark Kat and "Fungus-Fingers" by Mac. He could make himself amorphous to ooze under doors or onto the ceiling, and was capable of reforming himself after being blown up.
  • Mutants: A variety of animals and plants from around Megakat City, chiefly pet stores, transformed using a chemical called Katalyst X-63. Although they had no particular weakness, and were killable by conventional means, their mutation could be reversed using common anti-mutagens.

Unused Creatures

These creatures of Viper's appear only in unused premises or unfinished episodes.

  • Mega-Trees: A trio of giant plant monsters consisting of a sequoia, cactus and palm tree, which Viper used in his attempt to steal Katalyst 100 from Megakat Biochemical Labs. The cactus and palm could fire their needles and fronds like projectiles. The SWAT Kats defeated them by making them shoot one another accidentally, and destroyed the monstrous sequoia by firing Piranha Missiles down its throat. *Only used in Blowout!, the script which eventually became Katastrophe.*
  • Venus Trap Flies: A trio of half plant, half insect creatures used by Viper as his flunkies during his alliance with Dark Kat and the Metallikats. One was killed by Razor. The fate of the other two is unknown. *Only used in Blowout!*
  • Hedge Elephant: An ordinary hedge trimmed to resemble an elephant in the Megamusement Park's topiary garden, until Dr. Viper brought it to life to attack the SWAT Kats. It was accidentally killed by the Metallikats. *Only used in Blowout!*
  • Mutant Scarab: A giant, armored black beetle created by Viper when he used Super Katalyst S66 to transform the already mutated Dr. Harley Street. The creature possessed immense strength. It was simultaneously crushed and drowned in a battle with the SWAT Kats when they flooded the Megakat Thermonuclear Plant. *Only used in The Doctors of Doom, an unfinished premise intended to be the season two finale.*
  • Mutant Grub Worms: Huge, white armored worm like creatures created by transforming a group of kats Street had already converted into Ci-Kat-A like himself (Enforcer rookie Gray Taylor and a group of escaped convicts). They could dig through the earth very powerfully, and were killed along with the giant scarab in the flooded thermonuclear plant. *Only used in The Doctors of Doom.*



  • The episode Katastrophe was originally titled Blowout!, and depicted Viper with alternate creations to his mushroom monster; a trio of "mega-trees" (including, weirdly, a cactus monster), half-plant, half-insect creatures called "Venus trap-flies", and a living, animated hedge elephant from a topiary. Viper is also arrested by Commander Feral rather than apparently being blown up along with Dark Kat and the Metallikats.


           SWAT Kats Villains

Commander Ulysses Feral | Dr. Viper | Dark Kat | Pastmaster | Metallikats | Madkat | Morbulus | Hard Drive | Lieutenant Steel | Rex Shard | Mutilor | Lt. Traag | Turmoil | Katchu Picchu | Mummy Commandos | Chop Shop | Volcanus | Tiger Conklin | Dark SWAT Kats | Dark Callie Briggs | Lieter Greenbox | Zed