Paddy the Pelican Shorts
Calling these fifties-era, made-for-TV cartoon shorts cheap would be an insult to cheapness.
Apparently, they're based on a character who started out as a puppet on a Chicago-area kids' show. The black-and-white animation looks like a pencil test. The animation is nothing but endless loops over and over. One single man does every voice in the cartoon, and not only does he sound like he did his voice recording in a broom closet, the quality of his acting in general makes Tommy Wiseau sound like Sir Ian McKellen. The dialogue this "actor" is reading sounds as if he lost the cue cards just before recording started and is frantically ad-libbing to fill the characters' lip movements (you know, that "Speed Racer" style of dialogue). The only music is a few odd organ chords here and there--that, and a theme "song" (and I use the term generously) that is probably supposed to sound like a pelican squawking, but actually sounds like the Joker decided to embark on a singing career--after taking Valium. The backgrounds consist of a few distinguishing features here and there in mostly white space.
In short, any one of these shorts (most of which can be found on YouTube--I think there were only six) would be perfect for one of the live Rifftrax shows--either before a main feature, or as part of one of the shorts compilation shows.