To call for a certain wrestler to run in during a match, hold all four top buttons (L1+L2+R1+R2) and press a direction + a button. Each combination of a direction and a button corresponds to each of the 16 wrestlers in the game.

Note: it becomes a Handicap match with you and whoever you called in against your opponent, but no matter what happens, your opponent will win by Disqualification. Also, it can only be done in a 1-on-1 VS Match.