When the girls have a sleepover at Yo's, Fanboy believes they're aliens in disguise and he and Chum Chum sneak in on the fun.
Tropes:
- Alien Among Us: What Fanboy was led to believe.
- Ascended Extra: All of the girl characters have big roles in this episode.
- Blank White Eyes: Fanboy's Imagine Spot has all the girls with these.
- Blind Without 'Em: Fanboy knocks Nancy's glasses off when passing out invitations, causing her to not see well. Also, her eyes shrink.
- Captain Obvious: Chum Chum was right at Fanboy's initial response to what girls should do on Saturday nights ("To braid each other's hair and glue rhinestones to cookies?"), yet he gets pulled in to believe his predictions.
- Continuity Nod: When in disguise, Fanboy says he and Chum Chum come from West Apetown, which is the hometown of Chum Chum's cousin Muk Muk in "Moppy Dearest".
- Covered in Kisses: When FB and CC's disguises are revealed and they brace for the inevitable, they are relieved when their faces don't get eaten; instead, the girls kiss them all over with lipstick. The duo find this embarrassing and even worse, and they promptly flee the house in disgust.
- Credits Gag: The credits list Fanboy and Chum Chum's girl disguise names along with their own.
- The Cuckoo Lander Was Right: In the end, it turns out Fanboy's alien suspicion was right, only they eat heads instead. Too bad they didn't notice...
- Disguised in Drag: Fanboy and Chum Chum do this to get into Yo's Slumber party.
- Dumbass Has a Point: Chum Chum actually does have the perfect reason why Yo didn't invite them to the sleepover.
- Human Aliens: What Fanboy assumes the girls are. The ending reveals he's right after all.
- Lie Detector: Dollarnator becomes one.
- Paper-Thin Disguise: The boys' girl disguises, though they don't take off their superhero costumes.
- "Psycho" Strings: Plays when Yo opens a fridge revealing the heads of all of Fanboy and Chum Chum's male friends.
- Real After All: The girls really are aliens, though they don't eat faces, they eat heads.
- Right for the Wrong Reasons: When Yo throws a girls only slumber party, Fanboy assumes the girls are secretly face-eating aliens in disguise and he and Chum Chum enter the party in disguise to find some answers. When they get no proof and their disguises are eventually revealed, they are relieved when their faces don't get eaten, but are embarrassed when they get kissed instead, and they flee the house. Once out of sight however, Yo reveals they're not face-eating aliens as Fanboy predicted — they're head-eating aliens, meaning Fanboy was right about them being aliens all along, just with the wrong kind.
- Screw This, I'm Outta Here: Fanboy and Chum Chum are relieved when their faces aren't eaten, but when they see they were kissed all over instead, they deem it "even worse" and leave the party.
- Shout-Out:
- The movie with the vampire and zombie that the girls watch seems to be a parody of Twilight.
- Chum Chum's girl disguise is called "Chumbelina Jolie".
- Slumber Party: What Yo has for the episode.
- Snap Back: There is no mention of the girls as aliens after this episode, and all the boys have their heads back in return.
- Subverted Suspicion Aesop: The girls scoff at Fanboy accusing them of being face eating aliens. They're really head eating aliens.
- This Is the Part Where...: "This is the part where they eat our faces!"
- Wham Line: The very last scene.Francine: I can't believe they thought we were face-eating aliens.Yo: I know... we're HEAD-eating aliens!
- What Happened to the Mouse?: Dollarnator wasn't seen again after he leaves the party. Also, he never revealed his disguise.
