Revealing mistake: David and Del Fry are fighting after David gives Del Fry the shot. When showing the back of Del Fry, his hair is black not gray, revealing that it's a stuntman.
Revealing mistake: When the crew at Prometheus are viewing the tape of Hulk destroying the helicopter, it is obvious the tape is just stock footage from the scene earlier when the Hulk actually does destroy the helicopter. The camera angles used are exactly the same, and they are also angles the other crew wouldn't be able to film from.
Chosen answer: Bruce has always been the character's middle name. In the comics he is Robert Bruce Banner, here he is David Bruce Banner. Apparently the executives behind the show preferred the name David.