I am pretty sure everyone has seen Drugs are like that. Also why does it have to be one everyone knows? They will be showing the short when they riff it so everyone will see it.
I just got around to seeing Drugs Are Like That about a month ago. It took me about a year just to get the Rifftrax for DVD's I already owned, and I'm just now getting into the VOD side of things. I'm thinking that, if I want to continue to enjoy Rifftrax going forward, I'll have to start getting the VODs, though. The "riffing popular movies" model seems to be going by the wayside.
That said, D.A.L.T. was as good of a short as anything they did on MST3K. (Although "Money Talks" is still my favorite short of all time.)