I've thought about that myself before. If The Jim Henson Hour had lasted longer, Scott Bakula would have made a great guest. (In fact, the first episodes of QL ran immediately after JHH!) We already know Scott's got a great singing voice, and he was good at the comedic moments on the show too.
Hey, what if Angus MacDoogle (sp?) from the Star Wars episode of TMS returned to be a guest on JHH, and Scott "leaped" into him to save Kermit from a bad show? He could have Gonzo or Digit or Bunsen for his holographic Observer. (He could even have Beaker, though he wouldn't be able to understand what his mission was! "Mee mo mee mo mee mee..."