That's one of my favorite quotes from MST3K. Along with "It stinks" and "Rock climbing, Joel"

Whoops, I completely forgot to say what I thought of Mitchell. It was funny in spots, but there were lots of misses as well. Maybe it's because I'm too young and haven't watched nearly as much movies as those guys to know some of their jokes. Most of the enjoyment for me came by comparing it to the Blacksploitation films back then. I swear that thing is Whitesploitation.

mst3k is brilliant.

Overdrawn at the Memory Bank was one of my favorites simply because it was so patently ridiculous and surreal that I simply couldn't believe that this was a real honest-to-God sci-fi movie trying to take itself seriously. That and I'm a fan of Casablanca. There's so much abject silliness in that movie, and the MST3K crew did a great job with it.
Space Mutiny was beyond unbelievable. I couldn't believe my eyes: they were ripping off classic BSG footage! They even called their fighters "Raptors"! Not to mention the ridiculous "uniforms" for the women which looked they were hand-me-downs from The Running Man.
I never saw Mitchell, but I did see Final Justice. Man that movie was so boring.
Manos was indeed a challenge to watch (watching it gave me a migraine), but hearing Joel and 'Bots reaction to the infamous ending was priceless.

As others have already mentioned MST3K was a hit'n'miss kind of show. My sense of humor is adequately messed up that I find most MST3K episodes hilarious on an epic scale.
However, there are a few episodes that should be bumped to the top:
- Agent for H.A.R.M ("oh no, he's doing the ol' squish squash on my wind tube") and ("ACTION PANTS")
- Prince of Space ("I LIKE IT VERY MUCH") and ("I'm spinning the sallad")
- The Deadly Mantis ("I have a mantis in my pantis") and ("Looks like giant cross country skiers!")
- Pumaman ("This floor is made entirely of nougat") and ("hu-MA-MAN")
- Mitchell ("Liquid Metal!")
Honorable mentions:
- Hobgoblins
- Eegah
- Overdrawn at the memory bank
- Manos: Hand of fate (I actually laughed)
There's a ton more, but those were the ones that came into my mind right away.

Wow...favorite MST3K movies. Gotta think about this for a minute (and take a look at my collection to jog the memory) :
Mitchell
Space Mutiny
Angel's Revenge - Take Charlie's Angels, now make it lower budget and dumber. Oh, add a few bumbling Gilligan's Island cast members to the cast, too.
Merlin's Shop of Mystical Wonders - Watch as he sells deadly instruments of destruction to kids. Weeee!
Eegah - He's a cave man come back to life. It's sort of a love story.
Also, pretty much any of the Shorts that I've seen are fantastic. My personal favorite is probably the Industrial Arts one, though.