Actor Allusion: Possibly unintentional, but Gary Oldman's character Ruber (an obvious villain) is very similar to Dr. Smith, another obvious villain played by Oldman. It helps that both films came out in the same year.
Cary Elwes's voice work as Garret definitely evokes his performance as Westley in The Princess Bride, right down to a shot between him and Kayley that resembles that film's poster.
All-Star Cast: A big part of the voice cast were pretty big names.
The singers were no slouches either. Andrea Corr for Kayley or CÚline Dion for Lady Juliana are the best examples.
Even the non-English versions got pretty big names and talented voice actors and singers from each respective country. See the Your Mileage May Vary entry for details.
Breakaway Pop Hit: Few people realize that "The Prayer" was initially written for an unsuccessful animated film. Likewise, "Looking Through Your Eyes" was a surprisingly big radio hit relative to its origins, although it has mostly faded into obscurity since the film came out.
The actors mentioned above, but the film also features some famous musicians as the characters' singing voices: Andrea Corr of the Corrs as Kayley, Bryan White as Garret, Steve Perry as King Arthur, and Celine Dion as Lady Juliana.
There is also Sir John Gielgud as Merlin... who gets all of two lines. Why did they even bother? Granted, the story was more about Kayley and if he had gotten involved it would have been a major Curb-Stomp Battle...but at the same time one wonders why Merlin did absolutely nothing to help other than sending Ayden to find Excalibur (and, it's implied, to be Garret's friend and helper in the forest). Especially since, apparently, witches were involved in giving Ruber his potion. A lot more potential plot which would have actually justified casting such a well-known actor in the role...all gone to waste.
Non-Singing Voice: Most of the cast, possibly because this wasn't initially written as a musical, so whether a given performer could sing would not have been a concern at the time he/she was cast. In addition, some of the original actors can sing, but it's possible that the songs were added in so late that either the contracts were already set in stone or the actors were no longer available.
Old Shame: None of the animators who worked on this movie like it. Lauren Faust, who's staunch feminist philosophies are a complete 180 from this film's Unfortunate Implications, has been particularly brutal to it in recent years.
What Could Have Been: The film was originally intended to be darker, edgier and generally a more serious adventure as it was based on a very dark and serious book, The King's Damsel, before being retooled into a more family-friendly Disney-style production.