This is the first appearance of Luke McKeehan in the series.
Misspellings on the classroom blackboard: (a) "Grammer" and (b) "Detinshon" (for detention).
The arrow drawn on chalkboard behind Mr. Schidtler looks like it's going through his head.
It's obvious that a "Slurp" - a small blue character in white gloves - is equivalent to a Smurf.
In the theater scene, Kevin (nearly naked as Rocky Horror), Lisa (in Goth make-up as Magenta), Valerie (washing dishes) and Lance are all attending a showing of The Rocky Horror Picture Show where the song "The Time Warp" can be heard.