The greatest single sitcom episode in television history, imho.
You can find quite a few full episodes on Hulu, but, unfortunately, they've substituted "generic" songs for the rock originals that were initially in the shows due to copyright infringement claims (the producers didn't get perpetual rights to use those songs, so they had to be taken out after a few years -- that's one of the reasons the show isn't in heavy syndication these days). It makes a difference. For example, check out this clip starting at the 15:00 minute mark (it's the great "Les putting on a wig to get ready for his date with Jennifer" scene)
http://www.hulu.com/watch/291 Still funny, but the song in the original was Hot Blooded by Foreigner (the real song by the real band). Imagine how hilarious that was.