I think it was one of the coolest anti-drugs message to kids made, really! In the first part of the act, Pierce had to play drugs, but he did not want to be the bad guy and just got the kids to love him by being fun and crazy, whereas the other members of the skits were just boring the kids out of their mind. This was causing a kind of panic to the group, who really did not want their anti-drugs message to turn into a pro-drug message. Enters Chang, the crazy Chinese Spanish teacher, who took over the role: I think that the line "Did you expect me to stay the same forever? 'Cause that's not what drugs are, baby!" is pretty much the most relevant thing that can be said to kids. It looks fun at first, and then it stops being fun, but you're already in too deep and all. Name of the episode is Pharmacology, I think.