Art Nouveau: Several framed drawings by Aubrey Beardsley can be seen adorning the walls of Miss Piggy's Vogue Paris office.
Awesome, Dear Boy: When Chris Cooper was asked why he agreed to perform a rap song, his response was "Are you kidding? This is a Muppet movie! I'm in a movie with the Muppets! I'd have tapdanced in my underwear if they'd asked me to."
Creator Backlash: Sort of. Frank Oz – the original performer for Miss Piggy and Fozzie (among others) and probably the best-known Muppeteer who isn't Jim Henson – was offered a role in the film but declined, due in part to his own script treatment being passed over in favor of Segel's and a belief that the latter fails to "respect the characters" (although he still maintains it was flawed, he notably softened up). Some other, unnamed Muppet veterans have also expressed misgivings over certain elements of the film (e.g. Fozzie's fart shoes).
Deleted Scene: Good lord, do we need a Director's Cut! The movie was originally over two hours long! Several parts of the clips and previews shown before the release of the movie were not in the final cut, such as the Muppet farmer who performs at the start and end of Camilla's number, Gonzo knocking the bowling pin off Gary’s head, and various celebrities singing "Manha Manha" in various takes. Kermit doesn't introduce Camilla with the random, "... and now, dancing chickens!"
A scene which had the Muppets thrown in jail and featured Wanda Sykes and Danny Trejo was cut from the film. Judd Hirsch is only seen in the audience for a second and doesn't even say a thing!
Mary doesn't suggest going to lunch during Walter's drawn-out scream.
Walter's Dream Sequence was originally longer, and it shows, what with the rapid pace of that scene in the final cut! Since this was to be the first time the original Muppet characters would appear in the film, and wouldn't for the next 10-15 minutes following it, the writers probably wanted them to be silly around Walter's home longer.
DVD Commentary Features James Bobin (Director), Jason Segel (Gary, and co writer), and Nick Stoller (co-writer). Some nifty tidbits:
Jason Segel (Gary) was surprised that one of the choreographers was referring to Mickey Rooney as "Dad" as he told him where to move. Jason thought this was disrespectful of the older actor until he learned the choreographer, Michael Rooney, was in fact Mickey Rooney's son.
He also says he found it very hard to keep his eyes open when he looks up into the rain during "Man or a Muppet".
AND, the set at Kermit's house where he and Walter sit on the same couch: Jason sat down on the side of the couch where Walter's puppeteer would usually stand underneath, i.e.- a hole (where Walter is "sitting" in the scene in the movie). Jason fell into it. He was unhurt, and it took Amy Adams a long time to stop laughing.
The actress who played Walter’s prom date in the photo at the beginning of the film also appears as an extra during the Muppet Telethon and outside the Muppet Theater. Bobin joked that he likes to think that she’s still obsessed with Walter and followed him to Hollywood.
Sweetums’ scene at Mad Man Mooney and Sons was filmed at the same location as the car lot in The Muppet Movie.
James Bobin made a cameo (only seen from behind) as the director in the booth cuing the beginning of the telethon.
Hey, It's That Guy!: In grand Muppet tradition, far too many to count. If we listed them all, we'd be here all day.
Dave Goelz and Bill Barretta are the only Muppeteers in this film who originated their characters. By this point, Frank Oz had retired from being a Muppeteer for good.
The Other Darrin: This is the third Muppet film not to feature Frank Oz in any role note any new role, anyway; the original version of "Mahna Mahna" plays over the credits, with Frank's vocals as the Snowths intact, after It's a Very Merry Muppet Christmas Movie and The Muppets' Wizard of Oz, and the first in theaters. His characters are voiced and performed mostly by Eric Jacobson instead.
It's also the first not to feature Jerry Nelson at all. note Almost. Jerry recorded the opening announcement to the Muppets Telethon on the sly.
While a full list of replacements for each character would be too involved, a general guide to the Other Darrins is Eric Jacobson for Frank Oz, Matt Vogel for Jerry Nelson, and Dave Goelz remains, as ever, Dave Goelz. Jim Henson's characters are mostly divided between Steve Whitmire and Bill Baretta, and Richard Hunt's characters are divided between Steve Whitmire and David Rudman.
Recycled Script: This is the second Muppet movie involving the Muppets putting on a show to raise the money needed to save the theater from a businessman trying to tear it down (the first being It's a Very Merry Muppet Christmas Movie). However, despite the reused basic premise, they are totally different movies.
There have been conflicting reports though as to why Elmo wasn't allowed a cameo. The most common given reason is because Disney doesn't own any of the Sesame Street characters, and didn't want to pay royalties, or the producers of Sesame Street themselves didn't want to loan out Elmo. Kevin Clash, the voice of Elmo, said once that the real reason Elmo didn't appear in the movie was simply because he didn't like the script (for the same reasons Frank Oz didn't), and refused to reprise the role.
Gary was originally written as a ventriloquist with Walter as his animate puppet, but The Muppeteers and Disney didn't want the Muppets to be portrayed as puppets rather than living creatures.
They forbade the fact that Kermit was a millionaire in the early script and the mansion was waaaayyy bigger. It was rewritten to have the place built by Piggy when they were still together, but they broke up, and Kermit's been taking care of it ever since, so it's shabby and a bit ill-kempt in some places.
In early versions of the script Miss Piggy was to become a Lady Gaga type diva after the Muppets disbanded instead of a Vogue editor.
The end was different. Originally everything would be orchestrated by Kermit himself for putting the band together again by revealing that Tex would be Kermit in a human suit as part of a massive long-term scheme! But Disney said that ending would be too complicated for kids and the writers decided that was out-of-character for Kermit.
Molly Ringwald was written to appear, but ultimately couldn't. She does make it in in a way - she was crossed off a Rolodex card as one of the 80's celebrities Kermit calls to try to get a telethon guest.
During a sequence set in a prison, that ultimately ended up getting cut, Charles Grodin would've made a cameo reprising his role as Nicky Holiday. Sadly, he turned it down.
There was a scene in an early revision of the script in which one of the villains shot a gun, and everyone pretended to move in slow motion as a guy carried a Muppet bullet on a stick while making whooshing noises. Eventually Fozzie would burst in wondering what was going on, and would then start to move in slow motion too.
Walter's "human self" was initially envisioned as Michael Cera.
Working Title: The movie was originally gonna be called The Greatest Muppet Movie of All Time!!! And boy, did it deliver.
There was also The Muppets' Haunted House, first mentioned in 1996, mentioned again in 2001, and mentioned yet again in 2007, but ultimately was shelved in favor of The Muppets' Letters to Santa.
In 2006, Disney had announced that it had completed the pilot for a 10-episode TV series that was an X Meets Y of The Muppets meets The Office (US), which would have been a mockumentary series of how the Muppets work together to put on their shows. Like the above mentioned Haunted House special, it too was shelved shortly thereafter.
Fan Community Nickname: Muppet Freaks. Trivia status because although older and longtime Muppet fans have been using the term for a number of years, newer and younger fans, who are just getting into the franchise, may not be aware of this, and may be offended to be referred to as a "Muppet Freak".