Deliberate mistake: As usual when the Hulk reverts back into Bruce Banner, he is left wearing nothing but tattered pants. When Mitch McCutcheon sneaks Bruce Banner into the nuclear research facility, Banner is shown wearing his usual outfit of a gray collared shirt tucked into purple slacks that are intact. Given that the Hulk was just in the middle of the Nevada desert, Bruce Banner would be in no position to have a change of clothes on him, and the idea that the top secret facility would have an exact match of his go-to outfit is ludicrous.
Audio problem: When General Ross is shaking hands with Doc Samson and saying "Welcome aboard. I'll see you at the team briefing in the base hangar, five minutes," his mouth is closed for the first 8 words.
Audio problem: When General Ross interrupts Gabe Jones by saying "Will be under my exclusive command," his mouth is not moving for the word "exclusive."
Audio problem: When General Ross is saying to Major Talbot "If Nick Fury thinks he can just..." his mouth isn't moving.
Helping Hands, Iron Fist - S1-E4
Factual error: When Bruce Banner sees the Hollywood sign reflected in the puddle of water, the reflection is backwards.
Helping Hands, Iron Fist - S1-E4
Revealing mistake: When Iron Man appears on the screen in the Hulkbuster armor, if you look at the background behind him, there is a closed door behind him to his right and a control panel directly behind him, which means he appeared from out of nowhere.
Helping Hands, Iron Fist - S1-E4
Continuity mistake: Early in the Hulk's fight with Iron Man, he punches Iron Man onto the hood of a red car and then throws a blue car at him. Iron Man disappears from the screen as soon as the blue car hits the red car, and then can be seen either back on the hood, or instantly inside the car. If he is still on the hood, then he disappears from the screen once again when Hulk throws the car.
Helping Hands, Iron Fist - S1-E4
Continuity mistake: When Hulk punches Iron Man into the bus, Iron Man is shown landing through the roof in the middle third of the bus on the driver's side. When the shot changes to Iron Man inside the bus, the hole in the roof is now shown to be down the center of the bus and closer to the front.
Helping Hands, Iron Fist - S1-E4
Continuity mistake: After Rick Jones finds Bruce Banner among the overpass wreckage, Bruce starts transforming into the Hulk and grabs some gray rubble, which immediately turns the same color as his flesh.
Helping Hands, Iron Fist - S1-E4
Continuity mistake: When Rick Jones is hanging on to the containment unit that the Hulk is trapped inside, at one point the Iron Man gauntlet that he borrowed switches from his right hand to his left.
Helping Hands, Iron Fist - S1-E4
Continuity mistake: When Doc Samson is carrying the cylindrical tank for the nutrient bath, he is holding it from the bottom rim. When the shot changes, he is holding it from the outside.
Helping Hands, Iron Fist - S1-E4
Audio problem: When the S.H.I.E.L.D. helicopters land at Stark Industries, you can hear their rotors slow to a stop, but the animation still shows them to still be spinning.
Helping Hands, Iron Fist - S1-E4
Audio problem: When Gabe Jones has his back to the camera and is telling Ross where on the map that Hulk was going, his jaw is not moving at all.
Audio problem: When Talbot comes upon the Hulk in his helicopter, the helicopter doesn't make a sound until it appears on screen.
Continuity mistake: When Bruce Banner is in the soup kitchen, there are several paneled windows behind him. When he is shown standing up from his seat, it is only a brick wall behind him.
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.