I've been reading parts of Nightcrawler in comics and I get the feeling his characterization isn't consistent. I really don't see him as a happy-go-lucky flirtatious guy but more as a solemn serious mutant whose a strong catholic and the part I read him going to 'do it' with Amanda Sefton? He should know full well not to engage in sexual activity if he's not married. He threaten to kill someone even though killing is a sin in his religion. Either it was Claremont's doing or Nightcrawler was that way when he was first introduce.

Nightcrawler started out as a generally 'happy-go-lucky' guy. But as he started to become a popular character, the writers decided to give him some more character development and a more 3-dimensional personality. They decided that making him a devout Catholic with aspirations of becoming a priest would make him a more interesting character. Unfortunately, I don't believe Claremont or most of Nightcrawler's other developers were devout believers in God, and so their idea of how someone like Nightcrawler would act. Apparently they thought that threatening to kill people and having sex before marriage wouldn't be that big of a deal, even to a strong believer in God.

He grew up ostracised from society and was raised by a family of sorceresses.  He even had to teleport out of a bath with Amanda Sefton to save Candy Southern... and teleported them back into the bath landing on top of Amanda.  The priesthood thing came much later when someone thought that the Catholic demon was a good idea, without doing any research.

I think Nightcrawler was out of character in X-men the animated series that was aired in the nineties but I don't think I care because it sure suites him better.

Nightcrawler's  priest aspirations were something added to humanize him. His demon like appearance was making him a very  unpopular. They searched for about a year or so on what his cultural background could easily provide. Priesthood was the answer they found. This was done with all of the the second generation x men. Storm for example over the course of this time switched from the street punk to the model mutant citizen and they made a back story explaining that the punk thing was in the past.