Saved by the Bell S01E08 - Cream for a Day

When Screech inadvertently creates a zit removal cream in chemistry class, Zack decides to team up with him in order to mass produce it and market it to the students of Bayside High. It appears to work well, until the cream accidentally turns the person's face maroon. After selling some of the cream to Kelly the day before the school votes for homecoming queen, Zack fears that Kelly will never want to talk to him again when the side affects hits.