|~ Jellien Clones whenever mayonnaise is mentioned by anyone|
Jelliens are a hostile race of aliens created by and working for their Jellien Overlord. They appear alongside their leader as the main antagonists of the episode Planet of the Jellyfish in SpongeBob SquarePants.
There are two categories of Jelliens, the first being Jellien jellyfish created by the Jellien Overlord himself. They look just like a normal jellyfish, except they have large black eyes on their tops. They are also shown to have a set of sharp teeth, though their purpose is unknown as the Jellien Jellyfish always swallow their victims whole. Their tentacles don't sting. Jellien Jellyfish wait for unsuspecting victims to fall asleep, and then swallow said victim in order to create a copy of the victim. This is the creation process of the second type of Jellien: the Jellien Clone. As with Jellien Jellyfish, Jellien Clones look exactly like the person they are a copy of, with the exception of having completely black eyes. They also have many blue tendrils inside their mouths instead of tongues. The Clones emulate a few personality traits of the original victim but are mostly emotionless drones whose only drive is to perpetuate the spread of Jellien Jellyfish so that even more people get replaced with Jellien Clones. The only thing that evokes any sort of emotional response from a Jellien Clone is the mention of mayonnaise. Mayonnaise is the one weakness of all Jelliens, as direct contact with the delicious condiment will kill them, so talking about mayonnaise near a Jellien Clone will cause it to become extremely angry and shout, "NO MAYONNAISE!" Although the Jelliens appear to be able to thrive in any temperature, it's implied that they may prefer colder climates as the Jellien swarm is seen taking up residence in the Krusty Krab's freezer room after successfully taking over most of Bikini Bottom.
In the beginning of the episode, the Jellien Overlord is seen eating jellyfish and producing Jellien Jellyfish en masse to begin his plan to invade Bikini Bottom. Patrick is one of the first Bikini Bottomites to be caught by this wave of Jellien Jellyfish, as he was napping in Jellyfish fields when the invasion began. His clone, Jellien Patrick, encourages SpongeBob to help him capture Jellien Jellyfish and give them to everyone in town. SpongeBob, oblivious to his friend's condition, happily obliges, and almost everyone in Bikini Bottom is replaced with a Jellien Clone as a result.
The next day, SpongeBob remains completely unaware of what's been happening to everyone else, but he does notice that something is amiss when Jellien Krabs insists that there is no mayo at the Krusty Krab even though they just got a new shipment ot it yesterday. He then finds Jellien Patrick working the grill, and he gives the sponge a foreboding message: he's here to replace SpongeBob and all of his kind. Despite this, as well as some other behaviors that clearly aren't normal, SpongeBob doesn't notice the Jellien epidemic and goes into the freezer to find some mayo. He finds the mayo, but then sees the Jellien Overlord and finally realizes what happened to all his friends. Panicked, SpongeBob sneaks out of the Krusty Krab and gets chased by a horde of Jellien Clones, but is rescued by Sandy.
Sandy explains to SpongeBob that all they need to defeat the Jelliens is to find their weakness. SpongeBob points out that the Jelliens seem to hate mayonnaise, so Sandy suggests they try that. SpongeBob tells her that the Krusty Krab has plenty of mayo, but the path is blocked by Jellien Clones. Sandy, knowing that the Jelliens are simple-minded creatures, has SpongeBob and herself don sunglasses to cover their eyes so they look like Jellien Clones. They manage to blend in and get into the Krusty Krab without any trouble, but then SpongeBob accidentally blows their cover and the duo is forced to fight. SpongeBob grabs a bottle of mayo and squirts some at Jellian Krabs, instantly melting him. Excited and relieved that the mayo is indeed the Jelliens' weakness, SpongeBob keeps squirting the mayo and melting more Jellian Clones.
After melting the last of the Clones, SpongeBob and Sandy venture the freezer to deal with the Jellien Overlord and his Jellien Jellyfish. They manage to melt most of the Jellien Jellyfish, but the mayo freezes before they can melt the Jellien Overlord himself. Thinking fast, SpongeBob throws the mayo onto the Jellien Overlord and Sandy turns up the heat so it melts on him. Thus, the Jellien Overlord dies and all the Jellien Jellyfish die with him, ending the Jellien invasion permanently.
- The name "Jelien" is a portmanteau of "jellyfish" and "alien."
- The Jelliens are a parody of the aliens from Invasion of the Body Snatchers.