I know they aren't exactly "Muppets" per se, but considering they're part of the Jim Henson family, I could imagine a Dinosaur Train spoof:
First one:
(cut to a scene where the family's in a dinosaur museum)
LOIS: All right kids, now remember, do not spend more than $25 on gifts.
CHRIS: Yaaaay! I'm going to get me a Dinosaucers comic book! (laughs)
LOIS: Now, Peter, please watch Stewie for me while I go get drinks. Peter, are you listening to me? Peter? (we zoom away from a close-up Lois' face to reveal Peter and Stewie are gone) PETER, WHERE THE H*** ARE YOU?
(cut to a shot of Peter and Stewie on a kiddy train in the museum, singing the Dinosaur Train song)
PETER: (singing) Dinosaur train... dinosaur train... dinosaur train... dinosaur train... we're gonna riiiiiiiiiiiiiiiiide... the dinosaur train! (laughs)
LOIS: PETER! GET THE H*** OFF THAT TRAIN THIS INSTANT!
PETER: (dismayed) OK, Lois. Come on, Stewie, we're getting off the Dinosaur Train.
STEWIE: D*** YOU, VILE WOMAN!
Second one:
(we cut to Peter watching a National Geographic special on dinosaurs)
PETER: Man, learning about dinosaurs is better than spending time with them, like I did when I time-traveled to 65 million years ago.
(cut to a shot of the Dinosaur Train [in 2D form] traveling along tracks, and its passengers singing the "All Aboard" song)
DINOSAURS: (singing) All aboard... all aboard... (a thump sounds)
(everyone screams in a panic, as the train's going way too fast and hits a bump in the rails)
TINY: (in a panicked voice) We're going to crash! I'm scared!
SHINY: (in a groggy voice) I think I'm going to feel sick... I hate traveling fast!
DON: Whee! This is fun, isn't it, Buddy?
BUDDY: You said it, Don!
(cut to Peter in the engine)
PETER: Oh, c**p! How do I stop this thing? (looks at all the dials)
Ah, here's how to stop it! (He pulls the lever, but it's too late. The train flies off the rails and splashes into a lake. Thankfully, no one is seriously injured.)
MR. PTERANODON: Is everyone all right, Team Pteranodon?
BUDDY, TINY, & SHINY: (in groggy voices, feeling sick from the fast speed of the train) Yes, Dad.
DON: Let's go again! Let's go again!
PETER (to an angry Conductor): Listen, sir, I didn't know how to stop this thing. I'm from the future!
CONDUCTOR: (in an angry tone, and in Seth MacFarlane's voice instead of Ian James Corlett's) YEAH, THAT'S WHAT EVERYONE SAYS, IDIOT! NOW LOOK WHAT YOU'VE DONE TO MY TRAIN YOU... (shouts obscenities at Peter for 30 seconds, with a sped-up voice)
PETER: Geez, calm down! I was only trying to say I'm sorry.
CONDUCTOR: (still angry) NOW, GET THE H*** OFF MY TRAIN THIS INSTANT, YOU FAT TUB OF LARD!
PETER: (dismayed) Yes, sir.