Misspelling on the classroom blackboard: "basex" (basics).
Christine says those magic words "I don't know" as she introduces the opposites but does not suffer the slime.
When Barth's Burgery goes all natural, the name on the box of his all-mineral breakfast cereal is Whole Earth (which suggests what the flavor must be like).
The final seconds of the "Mandatory Beans" sketch with Lance and Alasdair were edited by Nickelodeon, removing the sound effect of Lance breaking wind. Toward the end of the series, fart jokes would become more common.