In the Arcade mode, go to the boxer you want and press c left + c up at the same time
Before you select your boxer in arcade mode, hold down the Left High Punch button. When you push the D-Pad in a specific direction, you'll choose 1 of 5 cornermen. If you hold down the Left High Punch, Low Block, and High Block buttons, you'll get a high pitched version of the Irish guy. He sort of sounds like a leprechaun.