Kan Tokumaru voices Oro in New Generation and 2nd Impact, Takashi Matsuyama voices him in 3rd Strike.
Yuji Ueda is the voice of Urien in 2nd Impact, Lawrence Bayne in 3rd Strike.
Name's the Same: In terms of Makoto's special moves, one of them (Hayate) is named after a swordsman from the Street Fighter EX series. She also shares her name with another incredibly strong female fighting game character, Makoto Nanaya.
Believe it or not, Dan was considered for Street Fighter III.
Sean was initially supposed to the only Ryu/Ken-type in Street Fighter III. If that would have remained, he may have still been wet behind the ears, but he probably wouldn't have been nerfed in 3rd Strike. Heck, he probably wouldn't be treated like a joke.
Gill's original design was to have him manipulate light and darkness. However, Capcom, for many reasons, decided to use the fire/ice alignment to showcase their spiffy new hardware. His secondary color is a reference to the original direction (but he still retains fire and ice control).
The development team planned to include Hugo in New Generation, but he had to be Dummied Out due to time constraints.
Shin Akuma might have possibly been planned to appear in 3rd Strike, as he has nearly complete Dummied Out code in the game and can be completely playable with a hack.
Remy's place in the roster could have been taken up by a character that used poisonous attacks, predating F.A.N.G.