Attachment
The North American version of the arcade release includes three exclusive characters unlocked by inputting codes on the character select screen. These characters include Evil Ryu, a near-clone character of Ryu who uses the same power as Akuma, and alternate versions of Dhalsim and Zangief that have movesets reminiscent of their appearances in Street Fighter II: Championship Edition, featuring the omission of numerous gameplay features including super combos, taunting and air blocking.
Contributed by thejeriahoross
In the international release of the SNES version, the name of the character Sodom was changed to Katana. In every other English release of the game, he is still called Sodom.
Contributed by ShyanVixen
In Guy's Metro City stage, if 1 or 2 female characters walk pass in front of Cody in the background, he'll give them a naughty glance which will make Jessica mad and smack his face.
Contributed by ProtoSnake
In the Japanese Arcade version of the game, Evil Ryu has a unique ending. This ending is not present in the English arcade release or console ports of the game, instead Evil Ryu and regular Ryu share the same ending.
Contributed by ProtoSnake
Attachment
There's a set of sprites for Zanigief which show him performing a backflip. However, they seem to be unfinished and go completely unused.
Contributed by ProtoSnake
Attachment
The background of Ken's stage holds multiple cameo appearances of Capcom characters as guests at Eliza's birthday party.

In addition to the cameo characters, Capcom's chairman and CEO Kenzo Tsujimoto also appears as the servant on the far right.

Furthermore, the teddy bear Strider Hiryu is holding is an homage to a deceased Capcom employee who worked on the cancelled SuperGrafx version of Strider.
Contributed by Mass Distraction