As the Hulk jumps out of the window in the Coliseum, we can clearly see Stuntman Manny Perry is playing the Hulk, and not Lou Ferrigno. While there were a few stunts in this series that required a stunt specialist, it seems that the production crew used a stuntman a lot of the time for the Hulk, be it running, standing on a rock etc.
As David is quoting a long line from Dr. Stewart's book to Dr. Stewart, it's obvious that he is reading his lines from a cue card, eye's scanning back and forth.
When the Cougars are playing the "Mustangs", game footage of the Bears vs the Colts is used, but when footage of the actors is used, the Mustangs helmet logo changes from a horse-shoe to an entirely different logo.
When the helmet was split in half, you can clearly see the smudge of green make up on the other half.
Despite the fact that the Hulk appears in front of a stadium full of people and what had to be a live TV audience, people still don't believe he exists in subsequent episodes.