The Give Yourself Goosebumps book where you end up consuming mutagenic food that either shrinks or enlarges you.
You're staying at your aunt's house when your parents goes on a trip to Europe, as much as you hate it. Because your cousins are making life hell during your stay — your older cousin Barney is a bully waiting to beat you up, while your younger cousin Dora keeps dragging you to play with her dolls. And your aunt, for some reason, insists that you say out from the basement.
So, avoiding Barney who intends to beat you to a pulp, you enter the basement and come across a fridge containing two items — a chocolate cake, and a jar of peanut butter. And then you realize you're quite hungry...
Beware your choice of snack — the eponymous peanut butter will make you shrink and be left at the mercy of rodents, lizards and Dora's hungry cat Puff, while the cake will enlarge you instead, which, while initially sounding ideal, will result in government agents and the local military mistaking you as a monster...
Beware of the Purple Peanut Butter provides examples of:
- Absent-Minded Professor: It turns out the peanut butter and chocolate cake are injected with an experimental serum from the local professor, Dr. Abbott, who have zero knowledge of reversing the effects. Seeking the doctor's help will either have you turning into a living magnet, shrinking until you disintegrate, the doctor shrinking himself, or in one ending, the two of you swapping bodies.
- All Animals Are Dogs: While shrunken, you can actually tame a giant-sized (from your perspective anyway) lizard by rubbing its belly. Said lizard even licks your hand like a puppy would, and in the good ending where you restore yourself to normal, you feed that lizard some crumbs from the chocolate cake and gain an obediant giant lizard as a pet!
- Attack of the 50-Foot Whatever: In contrast to the titular peanut butter, eating the other food item, a stale chocolate cake (which might be laced with a certain green substance) makes the reader gigantic as opposed to tiny.
- Exaggerated in one bad ending; you end up growing so insanely huge that your head reaches the stratosphere, and you suffocate in the depths of outer space!
- Big Brother Bully: Well, Barney is your cousin, but he still fits under this trope.
- The Bully: Your cousin Barney simply loves beating you up. Even in front of the neighbourhood kids, your aunt, your other cousin Dora... one of the first things he did is to strong-arm you into a game of Hide-and Seek where "if he finds you, he gets to pummel you".
- Call-Forward: The scenario where you encounter living dolls in Dora's dollhouse is one to the much later Give Yourself Goosebumps book Toy Terror: Batteries Included, whose main plot centered on toys coming to life.
- Cats Are Mean: Dora's cat Puff, who will chase after you in an attempt to devour you after you end up shrinking to the size of a mouse from eating the peanut butter.
- The Dog Bites Back: Your cousin Barney delights in bullying you for no reason at all, but there are occasions in the first storyline where you gain extreme strength from eating the cake and get to pummel him back. As well as one ending in the shrinking storyline with you being restored to human size with a dinosaur-sized lizard as a bodyguard.
- Down the Drain: After shrinking from eating the peanut butter, one of the outcomes have you being flushed into a sink by Dora, and you'll need to travel through the drain pipes and find a way out.
- Incredible Shrinking Man: This happens to the reader if they choose the Purple Peanut Butter. The cover art
◊ even demonstrates this trope. - Intercontinuity Crossover: While seeking for a way to reverse the peanut butter's shrinking effects, you can come across the titular object from Monster Blood. As always, you're expected to know the effects of consuming Monster Blood from reading that other book.
- "Freaky Friday" Flip: One ending where Dr. Abbott botches the shrink-reverse process have the two of you swapping bodies instead.
- Lemony Narrator: Granted, it's a GYG book, but the narrator of this issue is noticeably a bigger Deadpan Snarker than usual, from taunting the reader for choosing to obey their aunt's wishes to stay out the basement, to calling the reader a wimp for making wrong choices.Are you serious?
Are you really so wimpy you won't go into the basement? Just because your aunt and uncle told you to stay out of it? Just because it might be dangerous?
Get real! — (proceeds to tell the reader to go back and make the OTHER choice instead) - Literally Falling Through the Cracks: Should you end up eating the purple peanut butter, you will end up progressively shrinking until you're mistaken for a bug by your aunt and thrown into the sink - where you're promptly washed down the plughole.
- Living Toys: In one scenario from the shrinking storyline, you decide to hide in Dora's dollhouse, and realize the dolls are alive, where they are actually sentient and can come to life at will, but must remain motionless in the presence of humans.
- Painting the Medium: In one bad ending where the reader shrinks into nothingness, the book's accompanying text literally shrinks in it's last few words.You feel yourself growing smaller......smaller...... smaller... END
- Paranormal Mundane Item: The titular purple peanut butter, which makes you shrink, and a piece of cake that makes you grow in size.
- Rodents of Unusual Size: Subverted in the shrinking storyline. The rodent is regular-sized, but you've been shrunken by the peanut butter until you're smaller than your thumb. So from your perspective, you're fighting a giant rodent.
- Sauna of Death: In one bad ending, Arnold tried to reverse the cake's enlarging effects on you by having you enter a sauna. But it instead overheats, causin you to shrink into nothingness.
- Shout-Out:
- The book references Alice in Wonderland by the title at several points. Notably, you wonder if consuming the other food (chocolate cake or peanut butter?) could reverse the shrinking or growing effects, like what Alice did in her story.
- The scene under Living Toys is a nod to the then one-year-old movie Toy Story.
- Taken for Granite: This book takes it to the extreme with one ending where Effy the baker fails to reverse the effects of the chocolate cake, and instead turns you into a gingerbread man.
