In Monster Blood III, Evan grows to gigantic proportions (macrophilia) and shrinks, thanks to his nerdy cousin's chemistry set experiment (microphilia).
Cuckoo Clock of Doom contains strong infantilism and F/m undertones. The protagonist is caught in his underwear by his female friends, gets a spanking off-screen by his mom and —after he de-ages into a baby— winds up getting his diaper changed by his mom. Talk about getting crap past the radar...
Say Cheese and Die—Again has the protagonist (Craig) growing so fat that his clothes rip while his friend, Sherri, becomes so skinny that her skirt drops in public.
One of the short stories in the sixth collection ("The Nutcracker Nightmare," about a girl who's dragged to see "The Nutcracker Suite" onstage and discovers that her old babysitter — whom she hates for being boring — casts a spell that makes time slow down to ridiculous porportions) has the protagonist aging up to the point that her dress rips from her outgrowing it. You know, for kids.
The ending of Werewolf Skin, when the protagonists friend begins turning to a werewolf and digs her teeth to his flesh. Made even better by the fact that the protagonist becomes a werewolf too.
Chicken, Chicken features a drawn-out depiction of the protagonist (and her brother) transforming into the titular bird, complete with mental changes. The "shivery" feelings the descriptions gave this troper were one of the first big hints that she had a transformation fetish.
In Ghost Camp, the ghost campers seem to really, really enjoying screwing with the protagonists by turning invisible. Also, Lucy.
I just watched Chillology (The 3-part episode with Karlsville) and noticed how hot Karl was...
The girl on the cover of The Curse Of Camp Cold Lake is actually pretty hot. This troper never understood what others found so scary about that cover art.
One of the "bad ends" in Toy Terror: Batteries Included features a detailed description of the protagonist going through a machine that encases them in plastic, leaving them whole and intact, but 'dollified.'