When Mandy went to the Detention Dimension, she pulls off Grim's teaching clothes. But when you see her in the dimension, Grim's clothes are not seen.
Billy: Oh, my gosh, I killed Ms. Butterbean!!
Billy: (upon seeing the clowns) Aah! Clowns! They will destroy us a...!
Mandy: You see, Billy? When you do nice things to people, they die.
Irwin: YOU STOLE MY WOMAN!!
Billy's fear of clowns is brought up again.
The chant Mandy uses to get out of the Detention Dimension is most of the chorus of the Calypso/Reggae song, "Iko, Iko". (The full chorus would have the word's "Iko, Iko, Ande" right after the two "Hey Nows").
The twins Irwin and Billy took out to the Valentine's Day Dance in look similar to Parvati and Padma from Harry Potter and the Goblet of Fire.
At one point Grim holds up his scythe and calls it his doom-stick, a reference to the movie Army of Darkness, where Ash calls his shotgun a boom-stick.
In "The Most Greatest Love Story Ever Told Ever", Nergal Junior writes in a diary to "record his dark thoughts." A comic book character named Johnny C. from Johnny the Homicidal Maniac has a 'Die-Ary' in which he records his own disturbing thoughts.
the Kool-aid man makes a cameo in this episode
Episode Title: Detention X
It is a spoof of the radio program, "Demension X".