All-Star Cast: Between the Muppets themselves and all the cameos...
Including, behind the scenes, Tim Burton and John Landis, who were amongst the numerous people called in to operate the Muppets for the final number.
Deleted Scenes: Statler and Waldorf popping up at random points in the movie.
A slightly longer version of the Kermit-Fozzie dance number in the El Sleazo Cafe.
An extended version of Doc Hopper's commercial.
An extra verse in both "Movin' Right Along" and "I Hope That Something Better Comes Along."
A more in-depth version of the reading of the screenplay (including a reference to "a large yellow bird").
A longer conversation between Doc Hopper and Max before they encountered the rainbow-colored studebaker.
Gonzo's reasons for hitting Fozzie's studebaker were originally different. Doc Hopper, while eating breakfast in the back of his limousine, accidentally sprayed a bottle of maple syrup onto his clothes. He attempted to clean the mess up with some tissues, but those ultimately got stuck to his suit. Eventually, tissue-covered Doc somewhat resembled a giant chicken, which distracted Gonzo.
Kermit and Piggy on a Hawaiian honeymoon during the "Never Before, Never Again" montage.
Sam the Eagle appearing on a sign that reads "Keep America Clean."
In Memoriam: The movie is "dedicated to the memory and magic of Edgar Bergen", who'd died shortly after filming his cameo appearance in 1978, and who was a major influence on Jim's early work.
Reality Subtext: Edgar Bergen and Charlie McCarthy made their last appearance in the film - Henson was inspired to make the Muppets because of him. Bergen died not long after his scene was shot, and the film is dedicated to him.
Talking to Himself: One of the benefits of this and the other feature films was the opportunity it afforded for characters like Jim Henson's Kermit and Rowlf, Frank Oz's Piggy and Fozzie, etc., to interact in a way that wasn't always technically feasible on television.
Jim Henson wanted Doc Hopper to have a Heel–Face Turn at the end, but Frank Oz disagreed, and won out.
Max was initially a minor character. Austin Pendleton was offered the role, but initially turned it down, feeling the part was too small. Director James Frawley rewrote the Max character, and about a week later, convinced Pendleton to appear in the movie.
"Never Before, Never Again" was originally supposed to have been sung by Johnny Mathis. After Mathis recorded the song, Jim Henson figured it would be much funnier if Miss Piggy sang it. But Mathis' version of the song wouldn't go to waste - it was featured in the television special The Muppets Go Hollywood.