I mean, there could be many interesting plots, such as the following:
Kermit could introduce Miss Piggy to his "Sesame Street" friends. Miss Piggy could also patch things up with Big Bird, since Big Bird and Kermit the Frog are friends.
Statler and Waldorf could meet Oscar and be admired by his own heckling.
Lew Zealand could visit Ernie and discover the two are long lost cousins.
The muppets from "the Muppet Show" could interview the children on Sesame Street.
Cookie Monster and Animal could hang out with each other; Cookie Monster instructs Animal on how to do Monster-piece Theater.
Doc Hopper could give Scooter a job at his store.
Grover and Gonzo could hang out with each other and perform heroic events; Grover could pretend to be Super Grover and Gonzo could be the Great Gonzo shooting himself out of a cannon. Grover asks Gonzo if he can be shot of the cannon, and Gonzo says yes, only if Grover tells him how to be a superhero, and also how to the Mexican Waiter Dance.
Zoot becomes the waiter for the “Charlie’s Restaurant.”
Fozzie reprises his “good grief, the comedian’s a bear” bit with Gordon.
Gonzo tries to get Luis to fix his iron, which is as flat as a pancake because Thog sat on it.
Uncle Deadly and Mulch introduce themselves to the Count.