Continuity mistake: When the group first finishes filming, when everyone says "There's No Hope With Dope!" Zack points his index finger out twice in a row to the cameras, but then when watching the playback of the film, Zack only points once.
Continuity mistake: At the end when they finish the commercial, nothing at all is the same on the playback as what they showed them do. None was the same. The wording and also the places and stances everyone was doing. The entire thing was different in the playback.
Answer: Zack is always good for a sarcastic jibe. Lisa was written as the most fashion and make-up conscious of the Bayside High girls. She was also portrayed as serious and somewhat prissy. The "crack your makeup" comment was a throwaway line. Zack was suggesting Lisa doesn't often get overly excited for fear of having to reapply her face. The line is met by laughter and screeches from largely adolescent female audience that seem out of proportion to the humor. "Saved By the Bell" audiences were rather prone to such excessive ebullience for no apparent reason. The reaction didn't last long, and the scene moved on quickly.
Michael Albert
Yeah that doesn't make any sense.