Cassandra Truth: Averted with Carol (and later with Mike) when Greg insists the cigarettes aren't his, as they trust he wouldn't lie to them. Played straight at first with Mrs. Johnson, who accuses Carol of being in denial, until it's later revealed to her that he and Tommy switched jackets by mistake, to which Tommy's mother apologizes to Greg.
The Cobbler's Children Have No Shoes: The head of the anti-smoking committee's son is the one whose cigarettes got mixed up with Greg's letterman jacket. She ends up pretty much pulling his ear home.
Drugs Are Bad: Done with rare subtlety for this kind of moral. Greg takes a puff, coughs and decides this stuff just aint for him. And while Carol does join the anti-smoking committee, the mothers aren't portrayed as Knight Templar Parent types, just concerned about the dangers cigarettes pose to teenagers.
Very Special Episode: Averted, and quite beautifully. Greg does indeed take a puff and it's shown as a bad thing, but through Greg's own quick realization that he doesn't want to be smoking just to fit in. The guys in the band all smoke, but are still portrayed as reasonably friendly guys towards Greg even after he decides not to smoke.