Gumball becomes jealous of Leslie because he thinks he's dating Penny, and, in a twist on the usual "protagonist thinks his crush is dating someone else and gets jealous" story, the jealousy turns out to be a demon spirit that needs to be exorcised.
- Bond One-Liner: Gumball gives four to Leslie, the first three coming out badly after which he gives up and says a better one later.
- Big "WHY?!": Leslie's reaction after Gumball's jealous side leaves him to be eaten by slugs.
- Black Comedy: The content of Gumball's locker (weedkiller and herbicide) make it clear his jealous side was planning to kill Leslie, which it almost succeeds at by feeding him to slugs.
- Carnivore Confusion: Leslie tries to convince Penny that by eating vegetables, she's a traitor to plantkind, and should become a carnivore instead.
- Daydream Surprise: The episode opens on a sunny day with Gumball cheering on Penny for completing a cheerleading maneuver and her blowing a kiss. Except it's actually raining, the move Gumball applauded ended with Penny faceplanting, and Gumball just spilled ketchup on his shirt.
- A Day in the Limelight: For Leslie and Penny.
- Demonic Possession: Gumball's jealousy literally takes control of him and has to be exorcised like a demon.
- Door Dumb: Gumball tries to flee out a door to Mexico by running into it repeatedly, forgetting that the door opens inward or to even use the knob at all.
- Giving Them the Strip: Leslie gets away from jealous Gumball's deathtrap of bugs:Jealous Gumball: How did you get away?! I glued you to the bench!
Leslie: You glued my pot to the bench!
- Green-Eyed Monster: Gumball's envy leads to him being literally possessed by jealousy.
- If I Can't Have You...: Jealousy uses these exact words toward Penny before self-destructing.
- Just the Introduction to the Opposites: One scene with Leslie and Penny is a comical inversion of discussions about vegetarianism: Instead of telling Penny to only eat plants because of the way the food industry treats animals, Leslie tells her to only eat animals because of the way it treats plants (because they're both plants).
- Lame Comeback:Darwin: What's going on, is you've dragged me here to eat my lunch in the rain, so you can gawk at Penny like you do every day, even though you guys aren't even boyfriend and girlfriend!
Gumball: Oh yeah, well you like a s-swollen... traffic... cone.
- The Mirror Shows Your True Self: Even while possessed by jealousy, Gumball's regular self can be seen in a mirror and communicate by fogging up his side and writing on it:Darwin: "Writing... in revesre... is difficlut". Yeah, that's Gumball alright.
- Murder Is the Best Solution: One of Jealousy's solutions for dealing with Leslie involves weed killer.
- No Ontological Inertia: When a spirit of his concentrated jealously is rampaging, Gumball ceasing to be jealous makes the shockwave from an explosion it caused freeze in midair and disappear.
- Relative Error: Darwin and Gumball think Penny is so close to Leslie because they're dating. Besides the other obvious reason why this isn't true, it turns out they're cousins.
- Running Gag: Characters responding with a flat "Wow" to the things jealous Gumball does.
- Salt Solution: Parodied during Carrie's exorcism of Jealousy from Gumball, where she puts him inside a barrier made of pepper instead of salt, and it works until Penny breaks the circle.
- Self-Restraint: Inverted when Gumball somehow thinks he's wearing handcuffs until someone points out he's just holding his arms behind his head.
- Skyward Scream: Leslie shouts toward the sky in anguish after being covered in slugs.
- Talking to Themself: Gumball and his jealousy talk to each other several time, including the very first scene where jealousy shows up.
- Tempting Fate: "At least there's no crowbar!" (crowbar falls out of locker).
- Time for Plan B: Against his jealous side's advise, Gumball opens his locker to find it stuff full of herbicides and vandalized pictures of Leslie.Gumball: What is this?
Jealousy: Uh... Plan B?
- Wham Line:Penny: We're not dating, we're cousins!
- Yandere: While possessed by Jealousy, Gumball goes as far as trying to kill Leslie by feeding him to slugs, all because he believes that Leslie likes Penny.