The Return of the Beast: Part 1 - S1-E1
Factual error: When the Hulk jumps up and grabs on to the tail of the helicopter, he is somehow able to hang on to the tail while spinning the helicopter in a circle. Helicopters require a certain weight distribution in order to maintain stabilized flight. Someone of the Hulk's size and strength wouldn't be able to just hang on to the tail and spin the helicopter. He instead would bring the helicopter crashing down.
The Return of the Beast: Part 1 - S1-E1
Continuity mistake: When Banner is strapped to the chair and trying to resist transforming into the Hulk, the extent to how much he has transformed varies. Some shots will show his hands and head becoming larger, and the next shot will show him to instantly be back to normal proportions.
The Return of the Beast: Part 1 - S1-E1
Other mistake: When Talbot is grilling Banner for his relationship with Betty, when Banner is saying "Someone like you perhaps," the screen briefly constricts and then expands back to normal size, similar to a window on a computer screen being maximized.
The Return of the Beast: Part 1 - S1-E1
Continuity mistake: When General Ross is warning Banner that he is not bulletproof, an armed guard is flanked on either side of Banner. When the shot changes, the guard on Banner's left had suddenly moved several feet away.
The Return of the Beast: Part 1 - S1-E1
Continuity mistake: When Rick is telling his boss that he needs to leave work to help out a friend in a jam, he is standing next to the payphone, and when the shot changes, he is already several feet away sitting on his motorcycle and putting his helmet on.
The Return of the Beast: Part 1 - S1-E1
Audio problem: When Rick answers the payphone, his mouth isn't moving when he says "Ed's Garage."
The Return of the Beast: Part 1 - S1-E1
Continuity mistake: When the Hulk is trapped inside the containment unit and Betty calms him down, once he has reverted back to Bruce Banner, his hair is shown being blonde instead of brown.
The Return of the Beast: Part 1 - S1-E1
Audio problem: When the soldier is telling Talbot what Banner is doing with the power station, the soldier's mouth and jaw areas are not moving when his back is towards the camera.
The Return of the Beast: Part 1 - S1-E1
Continuity mistake: When General Ross is talking to Betty about the danger the Hulk presents to the world, the distance between them differs depending on the shot. One shot shows them standing close enough to hug each other, the next shot shows them instantly at arms' length apart.
Answer: The Hulk is a giant brute who smashes everything in his path when he is angry. In Ang Lee's "Hulk," General Ross, played by Sam Elliot, explains it to his daughter.