The mugger waiting at Korben's door is none other than Gothika 's and La Haine 's french filmmaker Mathieu Kassovitz.
The Mangalores' human disguises (and a lot of extras) are played by fashion models who worked with costume designer Jean-Paul Gaultier.
Fog, the nervous, stammering bellboy, is played by British stand-up comedian/occasional actor Lee Evans.
The larger of the two cops getting their lunch at McDonald's is played by Mac McDonald, well known (in the UK, at least) for playing Captain Frank Hollister, the ranking officer in charge of Red Dwarf.
Cast the Expert: Milla Jovovich is fluent in four languages, and so had little trouble learning the alien language written by Luc Besson. They were apparently able to have fluent conversations in the language by the end of filming.
Casting Gag: The man waiting impatiently at McDonald's is played by Mac McDonald.
Dungeonmaster's Girlfriend: Double Subverted. Luc Besson wanted his girlfriend to play Diva Plavalaguna, but she initially refused because she didn't want to complicate their relationship. It was only when the actress they hired backed out that she agreed. The movie also marked the end of Besson's relationship with Maïwenn, given he ditched her for the film's main actress, Milla Jovovich.
Dyeing for Your Art: Milla Jovovich's hair was to be dyed from its natural brown color to her character's signature orange color. However, due to the fact that her hair had to be re-dyed regularly to maintain the bright color, Milla's hair quickly became too damaged and broken to withstand the dye. Eventually a wig was created to match the color and style of Leeloo's hair, and was used for the remainder of the production.
British actor Gary Oldman plays Zorg, a character who speaks with an extremely exaggerated southern US twang (illustrated by the line "Leave them one crate. For the cause." which is so heavily accented it comes out sounding like "For the course.")
Also counts for Christopher Fairbank playing Professor Mactilburgh in an early scene. He's generally more well known as Moxey, a Scouser, in British comedy-drama Auf Wiedersehen, Pet.
Non-Singing Voice: Opera singer Inva Mula dubs the Diva's singing voice, while Maïwenn Le Besco portrays her. Reportedly Mula told the composer that the notes written for her were impossible, because the human voice cannot transition that way. The solution was for her to sing all the notes in isolation and then splice them together digitally.
Alert film buffs will note that Korben and Zorg never meet each other face to face. In an original draft of the script, Zorg would have faced Korben during the hotel evacuation, where the latter beat the crap out of the former for firing him and attacking Leeloo before stealing his ship (the ZF-1 was out of ammo, which resulted in Zorg's Villainous B So D). Zorg then survives the destruction of the hotel with the personal shield of the ZF-1, only to land in a massive glacier. He then calls his secretary to send another ship, only for the battery in his ZF-1 phone to fail. That ending is featured in the novalization.
All the societal elites that Ruby points out at the opera were originally going to have more to do during the shootout at the hotel.
Elizabeth Berkley auditioned for the role of Leeloo, but studios were reluctant to hire her after the disaster of Showgirls.
Ruby Rhod's name was originally Loc Rhod. The name appears in the original script and the novelisation.
A set of alien garbage collectors were created for a shot that was cut from the final film. A huge pile of garbage has gone uncollected, which is still referenced in the film. The creatures would have been seen holding sandwich boards saying 'on strike' beside the garbage.