Shrek cracks a mirror by looking into it and smiling: the scene is virtually identical to the same one featured in Mike Myers' Austin Powers films.
Donkey's line "I had my mouth open and everything" actually came from part of Eddie Murphy's "Delirious" routine.
And the line "I'm a donkey on the edge!" may be a reference to 48 Hrs.:
"I am your worst nightmare! A nigga with a badge!"
In the fourth movie, Donkey very poorly sings the final line of Whitney Houston's "Greatest Love Of All", a reference to Eddie Murphy's role as the incredibly untalented Randy Watson in Coming to America.
Shrek tells Donkey "You're going the right way for a smacked bottom". Austin Powers said the exact same thing to Madonna in the Beautiful Stranger video.
Blooper: In Shrek 2, when Fiona knocks out Prince Charming with a headbutt, he's seen seconds later perfectly fine throwing the wand to the Fairy Godmother. You could argue that he recovered quickly, but then a few minutes later, he's seen getting up from the headbutt.
Cash Cow Franchise: In the top 10 for "Highest grossing movie franchises of all time" list.
Creator Killer: One of the franchise's sources of fuel was all the snark, bitterness and derision directed towards Disney boss and Katzenberg's former superior Michael Eisner, including having Farquaad be a caricature of him; this movie was one of the multiple punches that eventually knocked Eisner out of the Mouse House in 2005 (nearly losing Pixar was the final punch to send him to the floor).
Gingy is puppeteered and voiced by a woman in each production. Averted in foreign dubs.
In Shrek 2, Doris is voiced by Larry King. In the Spanish dub, her voice is provided by sports journalist Michael Robinson.
Deleted Scene: One from the first film has Fiona meeting a Gypsy woman named Bib Fortuna (a reference to the Star Wars character of the same name), who would eventually become the Fairy Godmother. In this version Fiona is always an ogre, and Bib Fortuna gives her a potion that would make her beautiful, but tells her that she will alternate between her human and ogress forms until she finds true love. After that, she is whisked away by her dragon guardian and returned to the tower.
Also, The Other Wiki says that the filmmakers intended to show the "Happily Ever After"-Form of Dragon as a pink winged Mare in Shrek 2. They decided against it.
There was going to be a scene shortly after Shrek and Donkey get Fiona out of the dragon's keep that would involve them riding a mine cart like a roller coaster, complete with at least three references to Disneyland via the talking skull from Pirates of the Caribbean, the yeti from Matterhorn Bobsleds, and the Country Bears. The storyboards for this scene are included in the DVD.
After Shrek won the tournament in the first film, there was to be a scene where Farquaad explains the quest to Shrek and they're standing side-by-side to show their size comparison (explaining Shrek and Donkey's size jokes to Fiona later in the film). One was storyboard which Farquaad wish to turn Duloc into a more modern city with convenient stores and mini-malls.
It's difficult to imagine just how influential and popular Shrek was when it first came out, as just about every western animated feature has been influenced by its humor and style, not to mention "proving" that computer animation was the only way to go in the 21st century.
Genre-Killer: After the first film became a roaring success, it would take nearly a decade for non-ironic fairy tale movies, especially ones made by Disney, to be taken seriously again. It didn't help that, in the decade preceding Shrek, Disney had done nothing but blockbuster princess musicals following the box office underperformance of The Rescuers Down Under (which Katzenberg oversaw) and some of Disney's staff were losing interest in it at that point themselves, as evidenced by The Emperor's New Groove being a full-blown comedy and Atlantis: The Lost Empire being an adventure film.
Along with Blue Sky Studios' Ice Age, another hugely successful non-Disney CGI filmnote Disney would ironically obtain the rights to that film upon buying 20th Century Fox (Blue Sky's parent company) in March 2019, this film became the final nail in the coffin for traditional feature animation in America. Disney shooting themselves in the foot in their attempts to revive it then and later by putting those movies against guaranteed blockbusters didn't help.
Multiple Languages, Same Voice Actor: Antonio Banderas voices Puss in Boots in English and in both Spanish dubs, Latin American and European. Something interesting is that, while in English he speaks with an overt Spaniard accent, in the Spanish dubs he speaks with a somewhat exaggerated version of his natural accent from his hometown, Málaga, in southern Spain.
The Other Marty: Chris Farley was attached to Shrek early in its development, but after his death (and many story changes) the role went to Mike Myers, who then performed an odd same-actor version of this trope, switching to a Scottish accent partway through and re-recording already-done lines.
Permanent Placeholder: According to Word of God, the use of the Smash Mouth song "All Star" at the beginning of the first movie was only intended as test footage track to get the timing of the opening down - they planned to use an original composition for the final product. However, "All Star" worked so well that they kept it in.
Serendipity Writes the Plot: You'll notice that both times we visit the city of Duloc, the streets are completely empty and deserted. The crowd scenes were specifically written to take place indoors or in another confined location to save on rendering costs for large groups of characters all moving independently of one another.
The line "You're on your way to a smacked bottom" was improvised by Mike Myers after he got annoyed at one of the directors.
The scene where Princess Fiona burps was written after Cameron Diaz burped during a recording session after drinking Coca-Cola. Donkey's quip, "She's just as nasty as you are!" was what Eddie Murphy actually said to Myers in response.
The film was originally going to be produced by Steven Spielberg, be hand-drawn (and later on, motion-captured), and star Bill Murray as Shrek and Steve Martin as Donkey. Spielberg did however still serve as the executive producer for the film, albeit going uncredited.
The original script had Princess Fiona born an ogre to the late King and Queen of Duloc. They had her locked in the tower under the lie that she was "of such rare beauty" she was kidnapped. They died, and the kingdom was left under the rule of an ambitious regent (implied to be Farquaad). When she 'became of age' to ascend the throne she escaped the tower and encounters a witch named Bib Fortuna (a reference to the Star Wars character of the same name) - who has narrated the entire sequence through her tarot cards. She gave Fiona a potion which would make her beautiful; but Fortuna warns her the potion has a side effect - she will change between her human and ogress form until she finds her true love. Later she was whisked away by her dragon guardian and returned to the tower. This storyline was not adapted to keep the story simple, but is mentioned through the "witch" Fiona tells Donkey about.
Chris Farley was originally cast as Shrek and even recorded some dialogue. When Farley died, another SNL cast member got his part (Mike Myers). Initial reports were that the script was radically reworked after Farley's death and Myers was basically voicing a different character. However, this was proven false when a recording of Farley as Shrek was unearthed with dialogue largely similar to a scene in the finished film.
Janeane Garofalo was originally going to voice Fiona, but with the recasting of Shrek's voice actor, Fiona's voice and character were changed so she could contrast with Shrek better.
Paul McCartney originally was in talks to voice Rumplestiltskin, even going as far as having a musical number for him planned with a song written by McCartney himself.
An IMAX 3-D version that would have added an alternate ending was also planned to be released in either December 2001 or summer 2002, but was cancelled.
In the first movie, they wanted the crescent moon on Shrek's outhouse to be the DreamWorks logo moon. But the studio said no.
Shrek originally looked quite goofy◊ (it's the picture on the right).
Writer Revolt: Well, producer revolt. Former Disney CEO Jeffrey Katzenberg made this film as a great big "Screw you!" to his previous company and especially his former partner Michael Eisner, whom he loathed, after Eisner shot down many of Katzenberg's idea and later beat him out of the studio head position. It worked, seeing as how this film put DreamWorks on the map and ended up indirectly contributing to Eisner being let go by Disney.