After a yearly visit to the comet Twonkus-3, Jimmy unearths one of its species, a Twonkie, which Carl adopts as a pet, and soon enough the creature reproduces and has one for everyone in Retroville. But things soon get strange when hearing music causes the Twonkies to mutate into rampaging beasts, and it's up to Jimmy to stop them before they destroy Retroville.
Attack of the Twonkies provides examples of:
- Alphabet Song: Ms. Fowl sings one to her Twonkie, which causes it to mutate.Ms. Fowl: Oh, A is a letter that we all should know!
Without it, we can't spell ANT!
B is a letter that we all love so!
Without it, there'd be no BOTULISM! - Bittersweet Ending: The Twonkies are defeated and set back to Twonkus-3 just in time, and the grand opening concert goes off without a hitch. However, Jimmy didn't remember to send back Sheen's un-mutated Twonkie, and it eventually reproduces, meaning they are stuck with more Twonkies for at least another year.
- Bizarre Alien Reproduction: Twonkies reproduce asexually by coughing up litters of babies that take under a day to mature.
- Cassandra Truth: Jimmy's aware he's this, which is why he forbids Carl from showing Retroville the Twonkies, knowing everyone will be actively ignorant to his warnings as they were almost killed the last time. When Carl disobeys him anyway, nobody heeds his warning, as Jimmy bitterly remarks.Jimmy: I told [Carl] it was a bad idea, but did he listen? No, he didn't! Well he's just gonna have to help me go from door to door getting everyone's Twonkies and then sending them back to space!
- Character Development: For once, Jimmy is more cautious when dealing with alien lifeforms and believes they should be kept at and/or returned to their respective habitats. When Carl asks Jimmy if he could have the Twonkie as a pet, Jimmy deems it too dangerous, due to his encounter with the giant monster on the comet. He only reluctantly allows Carl to have it (due to his constant whining), but only for a day until he's able to send it back. Additionally, Jimmy strictly forbids Carl from showing Retroville the Twonkies for their own safety. When Carl disobeys said order and shows the town the Twonkies anyway, Jimmy is rightfully ticked off at Carl when he tries to pin the blame on him.
- Chekhov's Skill: Sheen's horrible singing is revealed to be the key to stopping the Twonkies and preventing them from mutating, as they consider it as anti-music which causes them to fall asleep.
- Continuity Nod: Carl's "Bending and Stretching" song uses the same melody as his "Folding and Hanging" song from "When Pants Attack" and the "Sitting and Singing" song from "The Mighty Wheezers".
- Death Glare: Jimmy gives one to Carl with a clenched fist towards his face when he tries to blame him for not warning him about how dangerous the Twonkies are (which he's already done, yet fell on deaf ears).
- Do Wrong, Right: Downplayed with Sam. When Carl arrives at the Candy Bar, declaring he is going to save everyone from the Twonkies, explaining they become ferocious upon hearing music, he prepares to destroy the Jukebox by pouring pure butterscotch in it. Sam tells him to stop, tossing him chocolate sauce to use instead since it is way more effective.
- Expy: Twonkies are clear parodies of Gremlins; they both start out as Ridiculously Cute Critters which mutate into violent, horrible monsters if certain conditions are met (eating after midnight for Mogwai/Gremlins and hearing music for Twonkies) who are also Explosive Breeders (though while the Mogwai/Gremlins only reproduce when they touch water, in the Twonkies' case it seems entirely random).
- Eye Color Change: The Twonkies' eyes turn completely black before they transform.
- The End... Or Is It?: Retroville is saved and everything is back to normal, but Jimmy can't help thinking he forgot something. Turns out, he forgot to send back Sheen's unmutated Twonkie, and it begins to reproduce and its offspring scamper off; the final shot of the episode is one of the reproduced Twonkies against a screen titled, "The end?"
- Extra-Long Episode: The fourth in the series after "The Eggpire Strikes Back", "Operation: Rescue Jet Fusion" and "Win, Lose and Kaboom!".
- Foreshadowing: When Goddard plays music from Jimmy's rocket to help them find their way back if they get lost, it causes a Twonkie giant to find them and nearly attack the source, foreshadowing what makes them rampage.
- Fluffy the Terrible: The Twonkies are adorable creatures who turn into vicious monsters when they hear music, prompting them to attack the source of the sound.
- Fusion Dance: Not seen, but when many mutated Twonkies are brought together they can merge into a much bigger Twonkie.
- Hollywood Tone-Deaf: Sheen is horrible at singing, enough for anyone nearby to cover their ears. It soon becomes useful in the climax as it caused his Twonkie to fall asleep instead of mutate.
- I Warned You: Jimmy tries to warn everyone about the Twonkies, but they don't listen. When they mutate into monsters from music, and they start blaming Carl for showing them the creatures, Jimmy finally lampshades the trope:Jimmy: Guys, this isn't the time for blame. If it were, I'd be saying stuff like "I tried to tell you!", and "Why didn't you jerks listen to me?"!
- Logo Joke: Paul forgets his line in the DNA Vanity Plate.
- Never My Fault: Carl tries to blame Jimmy for letting him keep one of the Twonkies and go rampant (to Jimmy's annoyance). In actuality, it was Carl's fault for disobeying Jimmy's orders in the first place by showing their school (and the town) the Twonkies, which Jimmy forbade him from doing so (mostly because Jimmy's aware all his warnings will fall on deaf ears). Adding to that, Jimmy had only reluctantly allowed Carl to keep the Twonkie for a day because of the latter's complaining. Needless to say, it's refreshing to see everyone angry at Carl instead of Jimmy this time.
- Noodle Incident: We never hear what song Butch sang to his Twonkie. He just says, "Just when I was learning to love again!"
- Oh, Crap!: Carl has this reaction when his Twonkie mutates and closes in on him.
- Race Against the Clock: Jimmy has to round up all the Twonkies and send them back to Twonkus-3 before it leaves Earth's orbit until next year.
- Running Gag: Cindy hoping she gets the big solo in the grand opening concert throughout the episode. At the end when it's Sheen who gets the solo, she's very livid.
- Spoofs "R" Us: Ventriloquist Dummies R Us, where Hugh ends up stopping at instead of the supermarket to purchase Flippy.
- Take Our Word for It: We never really get to see the Twonkies mutate onscreen, as they're always off-camera or obscured by an object before their bodies change.
