Did R. Crumb appear in Dirty Harry?

I just read on the IMDB forums (the bottom of the barrel of online forums - jeez!) that R. Crumb appeared as an extra in Dirty Harry. Supposedly he’s sitting in the “Roaring 20s” strip club in the scene where Harry is in there. Is this true?

I don’t think it’s very likely that I’d get an answer here, but I thought I’d post it on the off chance that someone who’s a trivia ace might be able to confirm it. Thanks.