David Banner, while working as a custodian at the same lab as Bruce, took the DNA of his own son and experimented on three dogs to see how his son's "disease" would be replicated. The three dogs became enlarged, muscular, monstrous, powerful and feral. Banner sent his mutated dogs to Betty Ross so they would slew and possibly eat her in an attempt to have Bruce unleash his "real son".
Encounter with Hulk and demise
As Bruce received a phone call from his father, he learned that the dogs are after Betty and would kill and devour her. Bruce became angry from this and, (in part to Glenn Talbot instigating with Bruce), became the Hulk. He went to Ross's aide and engaged in a vicious and feral battle with the radioactive canines. The two larger Gamma dogs engaged the Hulk in battle while the Gamma poodle terrorizes Betty who took refuge inside her SUV. While trying to get Ross, Hulk uses a fallen tree trunk to swat the poodle away. Hulk, the mastiff, and pitbull were locked in fierce battle. The Hulk manages to get the fight away from Ross and continues fighting the beasts further into the forest. The dogs have the Hulk pinned for a brief moment, only for Hulk to fight and even bite the mastiff's leg. The poodle bites down on Hulk's groin, actually hurting the Jade Giant. The Hulk then grabs the poodle by it's ears and slaps it. He then uses the poodle as a weapon and swings it at the mastiff. The Hulk then humorously lifts the pitbull up and punches it hard in the testicles. With the canines briefly discombobulated, the mastiff and pitbull corner Hulk, as they pounce towards him, he jumps upwards into the trees. The two dogs collide into each other. The dogs corner and leap on Hulk, the weight causing the tree to fall down. The fall gives Hulk a leg up as he slams a boulder in the pitbull's face, seemingly ending it. The poodle begins to go after Betty once more while Hulk is charged and leaped on by the mastiff. The Hulk, now angrier, thrusts his fist down the dog's throat. He then lifts it up and aggressively slams it down, before the dog can recover, Hulk then smashes it with his fists, causing a great spray of green blood. The poodle continues it's attempt in getting Betty. While distracted, the Hulk jumps up and body-slams the dog through the windshield, crushing it. Ross is face to face with the dead dog as Hulk then tosses it's melting corpse away from her. The dog then explodes in a green spray in the distance. The fight seems over and Hulk calms slightly, only to be blindsided by the pitbull. The Hulk punches, claws, and grabs at the creature's muzzle. The dog getting more intense, sinks it's teeth deeper in Hulk's flesh. Then with intense strength and anger, Hulk enlarges his trapezius and breaks the pitbull's jaws, letting out a pained yelp. Hulk then slams the beast onto the hood of Ross's SUV and in one swift move, shoves his hands into the dog's mouth and violently rips the canine apart once again causing a massive spray of green blood. Ross is left distrubed by the violent display and even at Hulk himself. Hulk, covered in injuries and gore, looks and snarls at Betty, then finally calms down near a lake and reverts back to Banner exhausted and proud of his battle. Despite the dogs powerful jaws and sharp claws, they were however no match for the Hulk.
Before they behave like any normal dogs and follow David everywhere apparently trained to do so. They even accompanied him at his janitorial job at the lab Bruce works and the hospital he was in. The three dogs are orient towards David Banner, and seem to be very obedient to him before and after their transformation. Post-transformation they have become more savage and intensely aggressive. While fighting the Hulk, they are incredibly relentless and after receiving deadly blows and punches from their adversary, they continue to fight until the Hulk slaughters them. However it is hinted by their creator, David Banner, that their lives were going to be cut short due to them being unstable from the Gamma radiation and nanomeds cultured from Bruce's DNA. It appears that their owner held no quarms of pitting them against the Hulk and doesn't seem concerned that they never return to him. When Betty first encounters David at his home in Oakland, he advises to her to "not look them in the eyes, they don't like to be looked in the eyes". Possibly in an attempt to frighten her or serve as foreshadowing his ill-will against her.
- The dogs were foreshadowed by the prologue, where Bruce is playing with a plush dog at the age of five. In the film proper, the dogs represent the loss of innocence.
- The concept of the dogs were taken from the cover of a 2000 issue of The Incredible Hulk.
- In the Director's Commentary, Ang Lee reveals that he wanted this scene to be very violent as the dogs were now considered monsters and that the Hulk shouldn't hold back in fighting and killing them.
- In the novelization and illustrated script the Hulk would have killed the dogs more viciously such as snapping one's back by jumping down on it ,used an uprooted tree to smash one through Betty's car, and squeezing another's head until it crushed in his hands.
- The dogs seem to represent how apathetic and callous David is, as it appears he cares little to none for his dogs (or any living beings) as he simply addresses them "dogs" in lieu of names. It's noted that he didn't hesitate to mutant them and never seemed concerned that they were killed.
- The dogs actually do have names (see above), according to both concept art and ILM animators who worked on animating their CGI models.
- Lily seems to be the alpha dog, as well as the only one who was focused on killing Betty, which means she was smart enough to chase after the person whom David really wanted to kill.