Doing It for the Art: Bruce Willis wasn't paid for the movie. His salary would have nearly doubled the film's budget, and he wanted to work with Gilliam badly enough that he opted for a cut of the box office receipts instead.
Christopher Melloni is playing a cop, again. With long hair for once.
Done in universe by Dr. Railly, when she sees Cole in a photograph from World War One, which was the first step to convincing her that Cole may be from the future.
Hey, It's That Voice!: Arthur Dent is a future scientist! I mean present. Which is still the future in real life. Who better to consult about time travel than a frequent customer of the Restaurant at the End of the Universe who spent a relaxing holiday in his own planet's Prehistory for a couple of years?
Playing Against Type: Along with Se7en, one of the movies that helped Brad Pitt break out of pure pretty-boy type-casting. Also, Bruce Willis's character is notably more frail than what he usually plays. This was the first movie where one of Bruce Willis' characters dies.