Just had an idea for a reunion special for MST, that would encompass all the on-air regulars for one last (ok, MAYBE last) movie.
Start with focus on Joel, driving down a highway or something. After a few seconds, in a flash of light, he vanishes.
Cut to Mike and the Bots' appartment (seen at the end of the last episode). They're debating...something or another...until in a flash of light, they too vanish.
They all appear on the rebuilt Sattellite of Love (maybe with Movie look, maybe the Sci-Fi look). When they're contacted by the Mads, we find it was the team of Observer...and an older (and maybe wiser) Dr. Erhardt that brought them together. An alliance of all the Mads think they have found the movie that would break humanity, and put all their chips on the table in sending it to both hosts and the Bots.
From there, whatever movie is chosen could be riffed upon.
Oh, and to get everything of the past included, maybe some temporal problem causes Crow and Tom's voices to change periodically, allowing both Weinstein and Murphy to play Tom in the ep, and both Bellieu and Corbett to play Crow in the ep.
Was just a thought that I wanted to bounce around.
EDIT: Possible movies they could do
Anything starring Hulk Hogan
Either version of "Attack of the 50 Foot Woman"
(even though it's Fish in a Barrell) "Plan 9 From Outer Space"
Battlefield: Earth
Hercules In New York (Sorry Governator)
And that's just a few off the top of my head.