Visible crew/equipment: In the episode when David is working in the arcade, when the two old men drive off to kill the man in the other car, the entire cast and crew, as well as the camera and camera man are reflected in the car.
Continuity mistake: When the lab is set on fire and the Hulk jumps into the room to save Elana, the Hulk that jumps through is actually a stunt double. Noted because the Hulk that jumps in isn't that tall.
Continuity mistake: When David gets out of his car and looks at the flat tire, the hubcap is gone. When he goes to the front and jacks the car up, he uses the jack handle to remove the hubcap that wasn't there before.
Continuity mistake: When Hulk throws a tree root at the helicopter, it smashes off the tail rotor. In the next couple shots, as the helicopter is spiralling down, we see the rotor is intact. (01:25:25)
Continuity mistake: The Hulk is offered some peanuts by a little girl which he takes with his right hand, yet they're in his left hand in the next shot.
Of Guilt, Models, and Murder - S1-E5
Continuity mistake: When The Hulk breaks free of the car getting crushed look closely. You can see Lou Ferrigno's palms aren't painted green like they are usually.
Terror in Times Square - S1-E6
Visible crew/equipment: When the two old guys drive off to kill the other man near the end, the entire crew, the camera and camera man are visible on the car doors.
Never Give a Trucker an Even Break - S1-E9
Continuity mistake: There is a scene where the female trucker is driving her truck and she intentionally hits a brown car. The problem is that she had already passed by this brown car a few seconds ago when David was getting into her truck through the window.
Never Give a Trucker an Even Break - S1-E9
Continuity mistake: When David is in the telephone booth trying to call the police he mentions that he can only read the first few digits of the phone number. Then there is a shot of the center of the dial which is almost all black and we cannot read any digit. A few seconds later another shot shows the center of the dial which is now white and we are able to read the first few digits.
Revealing mistake: Near the end of the episode, after the Hulk jumps from the wooden crate, he walks around barefoot. But right after the pickup hits the car, we can see that the Hulk is wearing green shoes to protect his feet.
Factual error: The story takes place in Galveston, Texas. The geographical area is flat, but if you look closely near the last hulk out, there are mountains in the background.
Continuity mistake: During the flashbacks of the abusive father's childhood his own father's shirt sleeves go back and forth from rolled up to just unbuttoned.
Revealing mistake: When The Hulk tosses the abusive father across the gym his blond hair looks fluffier and darker, indicating it's a wig on a stuntman.
Another Path - S2-E7
Continuity mistake: When the old Asian lady is hitting the Hulk using a wooden spoon, he is wearing brown pants. After escaping through the window, the Hulk is seen running on the street wearing blue jeans. But for the rest of his transformation he is wearing brown pants again.
Another Path - S2-E7
Revealing mistake: Mako's hair is obviously a wig, it's most noticeable towards the end, in the close ups when he's fighting the other man.
Revealing mistake: When the Hulk is inside the steam room and he throws his fists through the door, he loses fairly big patches of green make-up on both forearms in the process. (There is no CGI used in this 70s era TV show.)
Escape from Los Santos - S2-E11
Continuity mistake: During his second transformation, David tears his white shirt. When the Hulk is pulling Holly out of the cliff, the white shirt is nowhere to be seen. But when he takes her in his arms, he is wearing the torn white shirt.
Revealing mistake: When Adler fights with David close to the detonator just before his second transformation, the shots are filmed too close. It makes it really obvious that a stuntman is replacing David for most of the fight.
Continuity mistake: When Adler moves David into the barrel and loads him into the truck before his first transformation, David's head is at the bottom of the barrel. But when the Hulk emerges from the barrel he is already standing on his feet.
Continuity mistake: When Mike is on his balcony with Linda, we see that he is talking to 12 workers. But, in the next shot, a 13th worker wearing an orange hat and an olive green jacket magically appears almost completely to the right. However, when the 12 workers leave the area, the 13th worker cannot be seen anywhere.
Answer: An illness, although it's never stated what kind of illness. David blames his dad for her death because his father never took her to the hospital. So in all likelihood, her illness was never diagnosed anyways and David might not even have known what it was.
Bishop73