I'm surprised nobody's mentioned Sesame Street. Oscar is clearly a junky of some sort, I mean, the dude lives in a trash can. I think Snufflupagus was Big Bird's dealer or something, he's always waiting around for him. My guess is acid, Big Bird always looked like he was tripping. The Count is a pimp, but I doubt he's a dealer. The Cookie Monster is OBVIOUSLY stoned, seriously, all he wants to do is eat cookies. Elmo is rolling, I mean, he loves being tickled.
I haven't watched Sesame Street since I was 5, but I can still remember that they were obviously on drugs. I've been meaning to find out when it's on these days, and find one day when I have nothing to do, and sit around with a bunch of friends and get ridiculously stoned and watch it, I think it'd be hilarious.