The Fantastic Four (1994)
Roger Corman's unreleased (but easy to find) 1994 version of The Fantastic Four is rip for riffing!
Yes! Please do this! Corman made this 2 million dollars (of which apparently, 1.8 million went into someone's pocket) to keep the rights to the FF. This is prime riffing material!
This suggestion has been languishing too long.
Dave Gold commented
This could be done the same way the Star Wars Holiday Special was done.
Toyland Chairman commented
There's probably too many rights issues with this one, but it would be cool if the first official release was with Rifftrax.
Josh Faulkner commented
Here's a link to the Youtube version - I've seen better versions floating around, and if the guys did it, I'd recommend getting a better one...
Kevin Peregoy commented
Didn't they do this on MST3K? I thought I saw a Ron Howard documentary that said that.