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 2 - S1-E2
Other mistake: After the Abomination abducts Bruce Banner from the cavern, he causes a complete cave-in at the entrance. When Rick and Betty come to, they are able to see perfectly fine despite the sun being completely blocked out. Rick even states when he and Betty start to remove all the rocks that are blocking the opening that they need to find some blue sky before they can find Bruce.
Other mistake: When the Hulk takes down the S.H.I.E.L.D. helicopter, it is shown crashing to the ground with its pilot parachuting to the ground shortly after. However, the pilot was never seen ejecting and the helicopter's cockpit door was still closed when it crashed to the ground.
Other mistake: When Bruce Banner is attempting to rescue the nun from the fire, a beam falls from the ceiling and hits him in the head, triggering his transformation into the Hulk. Just before he starts his transformation, a set of green glowing eyes appear above his head. It appears the animators didn't properly sync the glowing eyes onto Banner's face.
Man to Man, Beast to Beast - S1-E6
Other mistake: When Gabriel Jones talks with General Ross, his fingernails are perfectly visible, even though he is wearing gloves.
Man to Man, Beast to Beast - S1-E6
Other mistake: When Banner snatches the tape recorder out of Langkowski's hands, the recorder stops playing without Banner pressing any of the buttons.
Other mistake: This show is in the same continuity as the Fantastic Four series from around the same time. However, in Fantastic Four, Dr. Doom has a German accent, and in this episode, he has a slight British accent.
Other mistake: When the forklift driver gets distracted by She-Hulk and crashes into the stack of metal vials full of flammable liquid, Bruce and She-Hulk don't hear any of the commotion until the explosion happens, even though they are only a few yards away. The crash and the falling metal vials should have been loud enough to alert them.
Other mistake: When Bruce Banner is sitting on the dock and recording his thoughts on a tape recorder, you can see that while his reflection's mouth is moving, his actual jaw is not.
And the Wind Cries... Wendigo - S1-E10
Other mistake: When General Ross is telling Hulk he will take care of Betty, he tells the Hulk he needs him to take care of the Wendigo. At this point in the episode, Ross doesn't know that the Wendigo is the creature that they are hunting.
Darkness and Light: Part 1 - S1-E11
Other mistake: When Gabe Jones is observing Doc Samson and Hulk emerging from the cave system in his rear view mirror, you can see his car is moving forward, but the image in the mirror remains the same size. (00:11:10)
Darkness and Light: Part 1 - S1-E11
Other mistake: When Doc Samson attacks the convoy, he begins by bursting his hands out of the asphalt. This is pretty illogical, as for him to be able to wait for the convoy to reach him and then break his hands through the asphalt at the right moment would mean he would have to be inside the road itself, which means there would have to be a void between the layer of asphalt and the surface beneath it large enough for a person to fit inside, which would be a hazard, as the weight of cars passing over would eventually cause this section of the street to collapse.
Darkness and Light: Part 1 - S1-E11
Other mistake: When Betty is trying to revive Bruce, a console explodes and a corridor is revealed that soldiers emerge from. It makes no sense for a heavy piece of machinery to be blocking the way into a corridor if blowing up the console is the only means of getting in or out.
Darkness and Light: Part 1 - S1-E11
Other mistake: When the Outcasts are launching boulders at the helicopters, they hit one that explodes immediately, and both occupants can be seen emerging from the fireball, safely parachuting to the ground. Even if they were able to jump from the helicopter before it exploded, their proximity to the explosion would have killed them before they had the chance to deploy their parachutes.
Darkness and Light: Part 1 - S1-E11
Other mistake: The river that Hulk battles Doc Samson in is only ankle-deep, but when Samson knocks Hulk out with the sonic gun, the river current is able to carry Hulk downstream. Hulk is lying flat on his back, and since the water is only ankle-deep, his back would be touching the floor of the river. In this case, the current of a shallow river would not be able to carry someone of the Hulk's mass.
Hulk of a Different Color - S2-E1
Other mistake: When Betty is watching surveillance footage of her father attacking the gray Hulk, the footage is same clips from earlier in the episode, camera angles, shot changes and all. Not to mention it's extremely unlikely she would happen to have surveillance cameras in the exact random area of the desert where the attack happened.
Other mistake: When She-Hulk is climbing the tree to speak to the Hulk inside the treehouse, you can see the doorway to the treehouse is barely large enough for her to fit through, so there's no way the Hulk could have fit through without damaging it. (00:06:06)
Other mistake: When She-Hulk is looking at her eyes in the mirror and raises her left hand to her face, only the hand in the reflection is raised. Her actual left hand doesn't raise.
Other mistake: When She-Hulk walks into her parents' house, they are shocked to discover her appearance. She-Hulk's identity as Jennifer Walters is public, as she is still a trial lawyer, and the previous episode showed that she has celebrity status. We know she and her parents aren't estranged, because moments before she tells the Hulk that they know about him, which she could only know if she kept in contact with them, so there's no conceivable way they could have been unaware of her transformation as well.
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.