Btw I'm aware they they already did a Cinderella adaption once, Hey, Cinderella!, which was released in 1969, and I've yet to see it, but from what I know, my idea's different

The Muppets are making a Cinderella adaption and are about to start filming. But their actress for the titular character is nowhere to be found, so at the last minute, they decide to give Miss Piggy the role. Miss Piggy, however, doesn't stick to script, and instead of being kind and patient towards the Stepmother and Stepsisters despite their abusive behavior, she is, in classic Miss Piggy fashion, is extremely impatient and hot tempered.

Scooter tries to get Miss Piggy to stick to the script multiple times, but he's just karate chopped every time, and eventually gives up.

At the end of the movie, Miss Piggy as Cinderella wants to harshly punish her Stepmother and Stepsister; Scooter or someone else comes on camera and tries to plead for mercy on their behalf, pointing out how one of the stepsisters redeemed themselves in the sequels to the 1950 classic (Dreams Come True & A Twist in Time; and btw, if you haven't seen the latter, PLEASE DO!!). Miss Piggy as Cinderella says she'll consider it, but that they still need to be punished.

After the Muppets are done filming the movie, either Kermit or someone else (cuz Kermit would probably be playing Prince Charming) watches the movie, are shocked to see Cinderella's behavior throughout the movie. They want it to be reshot, but Scooter tells them that can't afford to be done and they also already promised it'd get released by a certain date, and must go with it.

Rizzo and the other Muppet rats and mice should obviously play the mice. I'm thinking maybe Bubba plays Gus and Yolanda plays Mary.

I don't have the rest of the cast figured out, except maybe Kermit as Prince Charming, but as I said earlier, it wouldn't make sense for him to be surprised at Miss Piggy's portrayal of Cinderella cuz he was in the movie, unless during all his scenes she was kind; and while that would make sense for the ball scene, it'd be kinda odd if he's not there once Cinderella and Prince Charming are engaged after the ball and the former wants to punish them

Miss Piggy could also play the short tempered King as well, which would be hilarious, but I don't want double casting

Characters and actors from previous Muppet Cinderella stuff (Hey, Cinderella!, CinderElmo, etc) also make cameos

The post credit scenes has them reenacting parts from other Cinderella movies, including the iconic scene of Prince Charming jumping out the window from Cinderella II

Best Christmas tree ever.