I love the idea
of alternate reality episodes, but really haven't seen many, in large part because I don't watch much TV, and it's rare for non-genre shows to do 'em. When Scrubs started out, it seemed to zany and crazy that I hoped for wild stories like trips Mirror Universes and such, but alas, that was not to be.
... I wish that Smallville
had done some before going off the rails at the end of S3. I'd have particularly liked to see Clark travel to a reality in which he was female, and team up with his "twin sister" to take on a particularly nasty "meteor freak".
I imagine Early Edition
might have done one or two, but I don't know for sure.