I have gotten my mother into Red Dwarf recently, and we have been going through all of the series during our free time. Something just occurred to me that really sounds obvious the more I think about it: Kryten is Canadian. I don't know how, but he either was made in Canada by Canadian scientists, or created in the image of the Nice Canadian stereotype so that he would be able to preform optimal service.Either way, it explains his politeness and his non-British accent (never mind the first Kryten's accent).
It's not fully confirmed that Kryten is Canadian( From Wikipedia:"Most noticeably, whereas he previously had an "English butler" voice, he now spoke with what Llewellyn admits to be a bad Canadian accent."), but so many things point to it being the case. To explain the moments when the accent goes askew from it's Canadian roots: It's simply the effect of being around people who speak a different accent for so long.I look forward to seeing this develop as I continue to watch.
So what headcannons have you applied to your favorite shows?