Here's an idea I've had for awhile, so please keep an opened mind.
Disclaimer: The Muppets belong to Jim Henson and Disney, and the characters of My Little Pony: Friendship is Magic belongs to the Hub, Hasbro, and Lauren Faust.
The Pony Movie
Prologue: The First Screening
It was a bright shiny day at Hassis studios. A cart came up to the gate guard.
"Hello, I'm Flim." Flim said.
"I'm Flam." Flam added. "We're here to heckle The Pony Movie.
"Gentlemen, that's straight ahead." The guard said. "Private Screening Room B."
"Private screening?" Flim asked.
"Yeah, they're afraid to show it in public." Flam replied as the two laughed.
They then went onwards.
"Look at this place." Flim said. "What a dump."
In the screening room, Rarity, one of the stars of the movie, was talking to some of her friends.
"Yeah, I know, it was great." Rarity said with a smile as a creature named Discord appeared.
"Hey my dear, is this seat taken?" Discord asked as he snapped his fingers, and the seats next to Rarity flew away.
"Hey you, bring that back!" Rarity shouted out.
"Oh man, I'm so nervous." Rainbow Dash, another star said. "If I'm not funny, I won't be able to live with myself."
"Well then, you'll have to get another apartment, won't you?" Twilight said with a smile. As Rainbow Dash smiled too at the joke.
"You know, I heard that this movie is dynamite." Daring Do, a supporting actress in the film, said with a smile.
"Popcorn!" A supporting actress named Fluttershy said. "Fresh organic popcorn, only a buck."
"Oh honey, buy me some, please?" Cadence asked her boyfriend, Shining Armor.
"Oh sure." Shining Armor said. "Nothing's too good for my mare."
"Whoo!" Babs Seed called out. "This is gonna be awesome!"
"Whoa, easy there, Babs." A friend of Babs named Sweetie Belle said.
"Well I like the movie fine, so far." Flim said.
"It hasn't started yet." Flam pointed out.
"That's what I like about it." Flim added with a smirk as the two laughed.
Applejack, the host for the screening and one of the stars of the film walked down as he was stopped by Miss Harshwhinny.
"Applejack, does this film have culturally redeeming values?" Miss Harshwhinny asked.
"I certainly hope so, Miss Harshwhinny." Applejack said before turning to her good friend and co-star. "Howdy Rarity."
"Hello Applejack." Rarity said. "I tried to save you a seat, but someone took it."
"No worries." Applejack said as she got in front of everypony. "Okay everyone, welcome to the first screening of the Pony Movie."
Everyone cheered.
"Now before we begin, I'd like to give thanks to everyone who made this film possible. Starting with the hair dressers to the costume designers and-"
"Applejack, I don't think speeches are necessary." Rarity pointed out. "We can just watch the credits at the end. Roll the film."
"Well I just wanted t'thank-" Applejack began when Babs began shouting.
"ROLL THE FILM!"
"Okay, okay." Applejack said calmly. "Roll the film!"
Applejack then sat down to her younger sister, Applebloom, who had a red mane, a yellow coat, and orange eyes.
"Hey Applejack, is this how y'all really got started?" Applebloom asked.
"Well it's approximately what happened." Applejack said with a smile as they turned to the screen.
I know some of you will be angry with me mixing Muppets and Ponies, but I figured on giving it a shot, so don't be afraid to tell me what you think. Just please keep it PG.