Actor Allusion: Yzma is voiced by Eartha Kitt, who is well known for portraying one version of Catwoman. She displays an example of To the Batpole! and later gets transformed into a cat. A cute, but still demonic cat.
Completely Different Title: In Norway, the title is "A Kingdom for a Llama", because the word "groove" doesn't really have a good equivalent. Some merchandise does name it after its original title however (with "style" replacing "groove"), though the former mentioned remains the most known.
On his DVD commentary, director Mark Dindal grumbles about a minor example, claiming an executive at Disney forced him to include a particular The Wizard of OzShout-Out.
Also, Composer Meddling: Sting wrote a letter to the creative team, saying that he was pulling out of the film because the ending had Kuzco building the water park anyway and that entire plot was for naught because the protagonist didn't learn anything from his trials. The producers agreed with Sting's opinion and had the necessary changes made. In 'The Sweatbox', one of the creatives say that Disney movies are largely made via committee, with everyone having a say in how the final product is made, because of such situations: one person who normally would only be tangentially involved with the script might have an idea that changes the whole project for the better.
Related to Troubled Production: Mrs. "Sting", Trudie Styler, filmed a (slightly unfinished) documentary on the film's production, The Sweatbox. It was screened once, but since Disney owns this document of chaos, they make sure it never gets released (very likely due to there being a large amount of swearing in it), though it did end up being leaked on the internet in March 2012.
Related to What Could Have Been: Owen Wilson was originally cast as Pachanote who originally was designed to look like a twin of Kuzco...who, by the way, was called "Manco" in the original version. He recorded all his dialogue but when the film was retooled, his voice work was thrown out. There also used to be a short talking Incan statue sidekick to be voiced by Harvey Feinstein. Kronk was nowhere in the story. Yzma's original carnation was creepier, less neurotic, far more threatening, and obsessed with becoming young and beautiful again.
That's because both original Pacha and Lightning are voiced by Owen Wilson.
Marc Shaiman originally scored the film but had his work rejected after a test screening and was replaced by John Debney. Shaiman's work can be heard in The Sweatbox (the making-of documentary on the film and its Troubled Production). He describes his take as having too much Mickey Mousing.
The movie as made was supposed to end with Kuzco building his mansion on a hill further away from Pancha's village and inviting Pancha and his family to stay in it, before Sting pointed out that if Kuzco still built his mansion after all his experiences he wouldn't really have learned anything.