Shrek was loosely based on the book by Willian Steig and earned an 88% on Rotten Tomatoes. Steig was 83 when he wrote it. It is considered a great and has an awesome message for kids bout accepting and loving who you are.
The voice of Shrek originally was done by Chris Farley and they had recored something like 80% of the dialog before he unfortunately passed. At that point they brought in Mike Myers (without telling him he was replacing Chris) who decided to do a Scottish accent (fans of Mike Myers will remember all his Scottish characters) after seeing the first screening. Originally he did Shrek with a Canadian accent. Weirdly enough Steven Spielberg wanted Bill Murray and Steve Martin to do Shrek and Donkey. Dreamworks wanted to give the role to Nicolas Cage.
The film won the first ever Academy Award for Best Animated Feature beating out Monsters, Inc and Jimmy Neutron: Genius. It was originally conceived to by a live-action/CG hybrid but thankfully that idea failed to pass muster. Imaging what a bomb that would have been. The filmmakers and animators went as far as to take mud showers to best study the movement of mud. That's dedication.
Fearful of potential lawsuits Dreamworks showed the movie to the Disney lawyers. Disney was not happy with a lot of the jabs but deemed nothing in the film actionable. Disney did ban Radio Disney from playing any Shrek commercials.
The opening montage is set to Smashmouth's song All Star. Apparently that was originally just set there for the rough cut but the viewers loved it, leading them to license the rights from Smashmouth. Probably a good deal for the band.
The name Shrek in German (schreck) means "terror" or "fright". In Yiddish it means "monster". Kind of apropos. There is also a rumor floating around that Facebook founder Mark Zuckerberg took inspiration for his company logo from Lord Farquaad's logo on the castle banner. If true that is really weird.