i think movies like catalina caper and santa clause conquers the martians, and the fact that all the comedies mst3k did (even though there arent many) were amongst the more memorable episodes, prove that comedies can be riffed but it takes a special kind of stupid in the movie to be done right. like for one you cant improve on a good comdey much so they arent that riffable. imagine trying to tackle airplane or naked gun. and spoofs because theyre *meant* to be ridiculous and stupid i dont think can be riffed. that just leaves you with bad comedies but even then you gotta find the right ones. like i don't see dude wheres my car, little fockers or macgruber being riffed successfully even though they're bad. what it takes in a comedy for it to be riffable i think is not for the jokes to fail. its for the jokes to fail crash,burn, fall off a cliff, hit the rocks, drown, get pulled back up to the surface,and onto a beach, only then for the ambulance to fall in a trash compactor on the way to the hospital. its not just saying 'meh' to a bad joke or even 'that was stupid', but cringing and thinking"jesus christ did they really try and pull that?'. sort of a watching a train wreck thing. but even then the humor has to be bad in new and different ways to be able to get good material from a whole movie. thats where mst3k got the jokes from when they did comedies or made fun of jokes in the movie . thats why mk&b do puns in the riffing, not because they're funny in and of themselves but the'yre so bad and the fact that they do it in all seriousness, usually followed with a "go to hell mike" "already there Bill" that makes em funny. i think as far as a scale goes SCCTM would be a good movie to compare a comedy against to see if its riffable cause not only did mst3k do an awesome job with it, but cinematic titanic re-riffed it and it was still funny. like i said, a special kind of stupid.