My favorite MST episodes were probably the ones with the very bizarre foreign fantasy films (Jack Frost, The Magic Voyage of Sinbad, Santa Claus, Time of the Apes). I also always loved when shorts were shown, especially those cheesy 1950's educational films. I haven't seen every episode, but out of the ones I have seen, if I had to choose a least favorite I would probably go with The Beast of Yucca Flats. Even with Mike and the bots riffing, I have trouble getting through the film. Haven't seen very many episodes from season 1 or many of the rare episodes from the KTMA era, but of the few I have seen, they seem very slow-moving. It's obvious that at the time, Joel and co. were still figuring out just how many jokes they could fit in one minute.