An Aesop: Practical jokes have their place as long as they're in good taste ... but even then things can go too far.
Butt-Monkey: Alice, for several of Jan’s jokes. She becomes her own butt monkey in the final scene when she outsmarts herself, thinking a real ink stain on her uniform is Jan playing one last joke.
Marcia, Cindy and Carol are not happy about Greg bringing one home for his science project. Jan, on the other hand, finds him super cute...as well as a good way to scare her sisters. Marcia and Cindy change their minds by the end of the episode, though.
Alice, on the other hand, is extremely afraid of mice and calls the exterminator when she sees the mouse, unknowing whether it is Greg's science project or if the house is overrun by mice.
"Everybody Laughs" Ending: Except for Robert Reed, who wrote a lengthy critique about why he thought said scene — Alice outsmarting herself over the ink stain on the uniform — was inane bullshit. Said critique was published in Barry Williams’ autobiography "I Was a Teenaged Greg."
Humiliation Conga: Alice, when she realizes the supposed gag ink stain is a real ink stain.
Idiot Ball: Alice, who in the tag scene apparently cannot tell a gag ink stain from the real thing ... and one of her uniforms is ruined as a result; she thinks Jan was still full of practical joking fun and had placed the stain there ... only to find she had left an ink pen with the cap off inside the pocket.
This particular scene led to Robert Reed accusing the writers of making Alice a complete idiot for a joke he didn't find funny at all.
My God, What Have I Done?: When Jan realizes her latest joke might have gotten Marlon the mouse exterminated and could cause Greg to fail a science project that would have a major effect on his grade.
