The original Xbox design borrowed heavily from Sega's Dreamcast - in particular, the controller's unique VMU (visual memory unit).
The original Xbox's controller was designed for people with gigantic bear hands. Not being particularly well-received by the gaming public, a slimmed down redesign allowed people with regular-sized hands use the console. Eventually, the 360 came out and had (and still has) one of the best-designed video game controllers ever (or the worst, if you are a Sony fan). But before we got to that original bear-sized controller, Microsoft went through a lot of iterations, seemingly inspired by the Sega Dreamcast.
Seamus Blackley, one of the key people involved in the creation of the original Xbox has shared with us some of these early designs, dating all the way back to 1999. Check them out below:
Pretty interesting, right? I like the "X-wing" design in particular, but honestly, none of the concepts look like they would be particularly comfortable. I feel like all controllers from the N64/Dreamcast era had this big bulky uncomfortable feel about them for some reason.