Apparently, the ending to Egg Monsters from Mars just charged on through, to the point where even the fact that the male protagonist has a female name.
The cover alone for My Hairiest Adventure (book #26) is just ripe for sarcastic, immature book bloggers to make jokes about the myth that masturbation causes hairy palms.
My Hairiest Adventure also seems a heck of a lot like a metaphor for puberty—he's getting weird dark hair everywhere, it grows back after he tries to shave it off...It turns out that he's actually a dog, and the serum he had to be injected with was a failed experiment in turning dogs into children.
Then, there's the sequence where Lucy reveals to Harry that everyone in camp is a ghost and the only way to escape is to get inside a human body. The subtext of that sequence plays out like Harry is being raped.
And, on the non-sexual side of Getting Crap Past the Radar, Ghost Camp had a lot of scenes of kids doing violent things and not getting hurt (i.e., Lucy sticking her arm in a fire to get Harry's fallen hot dog, a girl getting decapitated from a soccer ball, a boy jamming a fork in his neck, Lucy pretending to drown to scare Harry, and a boy's foot getting impaled by a tent stake).
If an older audience reads "Piano Lessons Can Be Murder," Dr Shreek can easily come off as a pedophile (and the TV version of the episode does nothing to tone it down. They may have changed Dr. Shreek from being a robot to being a mad man haunted by the ghost of his mother, but the pedophilia undertones were there).
Ricky's revenge plot against resident Alpha Bitch Tasha in Calling All Creeps! is more or less the same idea as writing "For a good time, call..." on the bathroom wall.
RL Stine has said that it was indeed inspired by something like that which happened in College.
The last leg of Be Careful What You Wish For puts in as much Les Yay as you can get away with in a 90's children's book. After Samantha wishes for Judith to become her friend, the latter instead develops what appears to be an...unhealthy obsessionfor her. Judith carries Sam's books, wears the same clothes as her, waits by her house in the morning just so she can walk to school with her, and sneaks into her room during the night.
Much later, I Live In Your Basement had a similar stalker relationship with two boys instead. Also people turn inside-out in a fair amount of detail.
Read Monster Blood (the first one) as an adult (or post-adolescent with an immature sense of humor) and look for the implications of puberty (the constant references to "growing" and "feeling something weird and sticky" while Evan sleeps), masturbation (one scene had Evan trapped in a bathtub of Monster Blood and the way his struggle to get out of the tub was written, it sounded like Evan was on A Date with Rosie Palms), and Unresolved Sexual Tension between Evan and Andy (who's a girl).
Also read Stay Out of the Basement, where most of the lines (when taken out of context) allude to being "in the closet," being "out of the closet," "going down there" (referring to the basement), "experimenting," and fights over paternity (the clones of Dr. Brewster arguing amongst themselves over who's Margaret and Casey's real father).
Recurring antagonist Slappy, the evil ventriloquist dummy, hits and attempts to enslave children in all of his appearances and seems to have a weird thing about twelve-year-old girls.