In the scene that takes place right before the big game with Georgia Tech (the game Rudy plays in), the stadium shows the Penn State Blue Band on the field playing the Penn State fight song. The game then starts and Notre Dame is playing Georgia tech.
One of the fans in the stands is actually Daniel "Rudy" Ruettiger. He can be seen in the last few minutes of the film wearing a dark colored coat with a thick, light colored collar/lapel. Seconds after the actor playing Rudy runs onto the field near the end of the final game, you can see the real Rudy sitting directly behind the actress playing Rudy's mother. Then about 15 seconds after the game ending tackle, the actor playing Rudy's father turns around and grabs the real Rudy by the coat collar/lapel, then slaps his chest in joyful celebration.