@Shoryu...is the swearing really necessary? The closest Undyne comes to swearing in game is during that whole grass/grooty phone call.
grass/grooty? Aaaand, I dunno actually >3> Considering the content of most animes, and her history of all but 'injecting' anime directly into her blood-stream, It seemed viable. Granted, I could probably have replaced a couple of those... come to think of it, I don't even remember if there was swearing in Undertale...
Of course, I'm also someone who doesn't look at this 'set of words commonly labeled as swears/curses' as most people look at them... They're just words, They have normal meanings, and slang meanings, and Where I grew up such words generally had a slang meaning of 'completely standard expression of either insult, anger, shock, praise, or excitement, or any number of other things depending on the tone of voice.'
Don't get me wrong, I have no intention of turning her into a swear obsessed lunatic that'll say 'fuckin' 3-5 times in one sentence... I 'know' one of those and grates my nerves.
It just struck me that the 'last' thing on her mind while fighting something, or... at all really, save for moments where control is expected, would be 'is my language clean enough for a situation where I'm stabbing pointy objects into things?'. XD