Something that happens on TV and movies, what is it? (see details)

A bit like an inconsistency, but I think there’s another word for it. I’m pretty sure it’s on TV Tropes, but I’m not quite finding it. Here’s an example of what I’m talking about;

In the first Halloween movie, Laurie manages to poke Myers in the eye with a coat hanger, and he passes out. In the second movie, he grabs a nurse’s head and dunks her into a therapeutic bath tub with boiling water. Her face gets all boiled off and it’s all nasty. The thing here is, while Myers is keeping the girl’s head in the water, half of his arm is in there and he doesn’t even flinch. No damage to his arm, either.
So, he can withstand boiling water, but he gets knocked out by a coat hanger? What would one call this sort of loophole/inconsistency?

Another example. In Xena Warrior Princess, Xena is fighting off all these dudes at once, and someone from afar shoots an arrow at her. He’s aiming behind her head. Without even turning around, she catches the arrow in her hand just in time. Yet, in another episode, she’s alone in the woods at night, it’s all silent, and she gets caught off guard by some peasant.
So she can catch arrows in the midst of battle but gets surprised by random normal dudes in the woods? What’s the word for this?
Also, feel free to give your own examples of this situation, should be quite interesting.