Disney animated classics
You know the sort—Cinderella, The Lion King, any of those movies everyone knows and loves (unless they're a parent listening to it twice a day).
You know which Disney movies really deserve to be riffed? The direct-to-video sequels, such as "Cinderella II: Dreams Come True" and "Cinderella III: A Twist In Time". The sooner the direct-to-video sequels get RiffTrax, the better.
Ian Neumann commented
Come on, Rifftrax, MST3K didn't riff on any classic cartoons. Maybe this could be your big chance! :D