To select your opponent's character, hold start down for about 3 seconds on Draco. To enable random select, hold down start for about 3 seconds on The blue haired woman in the front row.

To make all the characters look like the elephant, hold start for 3 seconds on the elephant.

To play as Carbankle, hold START for about 5 seconds on Arle, and to play as Satan, hold start for about 5 seconds on Schezo (the white haired guy)