Overall the show promotes the importance of friends and family -- even if those friends and family members frequently bicker with each other or make mistakes. That said, the show also presents pot smoking as a normal activity and doesn't bat an eye at teen sex.
Slapstick at most.
The characters think and talk about sex a lot. Not too much is shown, but much is alluded to. Donna and Eric eventually have a lot of sex, and Kelso in particular is a very active teenage male.
Mr. Forman curses quite a bit, using words like "damn," "hell," and "son-of-a-bitch."
Drinking, Drugs & Smoking
"Mysterious" smoke clouds appear in the basement, and it's clear that the kids are smoking pot. Dad Red drinks beer regularly.