fangirl armor
Similar to plot armor. Refers to when a (typically male) character from film/television/etc has a large following of fangirls, and thus is incapable of being permanently killed in their movie/show/etc, because its writers know that said fangirls would riot if he did.
Guy A: How the heck is Castiel still alive?
Guy B: He's got serious fangirl armor.
Guy B: He's got serious fangirl armor.