One is a negative example:
Various characters are discussing how crazy Loki is, and Thor says, “Have a care; he is of Asgard, etc. etc. and he is my brother.”
The Widow points out all the people Loki has killed, and Thor immediately says, “He’s adopted.”
This would be a perfectly fine line from Malcolm Reynolds on Firefly, but it’s really wrong for Thor. It’s sort of like holding up a sign saying, “Joss Whedon wrote this screenplay.”
The positive example is from earlier in the picture, when Loki is being transported as a prisoner. Thor shows up, grabs Loki, and flies off. Cap is about to give chase, but Natasha advises him not to, saying that Thor and Loki are basically gods.
“There’s only one God, ma’am, and I’m pretty sure he doesn’t dress like that,” is Cap’s reply as he straps on his parachute.
Joss Whedon is an atheist and he got some flack for the line, but:
1) It’s not written for Joss Whedon; it’s written for Steve Rogers, who is not an atheist, and
2) it’s a really sharp line.
So, that’s today’s storytelling lesson from the movies. No matter how clever you think a line is, don’t put it in the mouth of a character who wouldn’t say those words.