Actor Richard da Costa (Luggage) is also the Librarian as an orangutan. He studied real orangutans in a zoo to learn how they moved.
Many of the angry mob of Star People outside Unseen University, and the customers in the Broken Drum during the fight scene, are Discworld fans recruited through fan websites and mailing lists.
Like Vadim Jean's previous Discworld film (Hogfather (2006) (TV)), there problems with the set flooding due to heavy rainfall while filming indoors.
Both Sean Astin (Twoflower) and Sir David Jason (Rincewind) are long-term Pratchett fans. Jason named The Colour of Magic as his choice of favourite book of all time in the BBC's Big Read survey.
Richard da Costa never got any actual screen time in human form, he was either in the Librarian's Organ Utan suit or inside the Luggage. He was almost filmed as a comedy mime artist (he had been to make-up and wardrobe) but in the end there wasn't time to shoot that scene.
The colors of the pattern on Twoflower's shirt aren't as garish as the description in the book, but they had to be chosen to avoid primary colors, or they'd have vanished in the blue-screen/green-screen sequences.
The Alchemist is played by Richard Woolfe -- better known for being Director of Programming for Sky One, Sky Two and Sky Three. Sky Televison commissioned the production of both "The Colour of Magic" and "Hogfather".