I have so many questions... I wonder how the legalities of this work. If people write in "Count Binface" or if that's the name on the ballot, then if he wins, does that mean Jonathan David Harvey (the actual name of the guy who plays him) is elected? Does Count Binface count as an alias? If not, he required to use that name while in office - or more precisely, is he not considered a member if he goes by his own name?…
If people commonly use it to refer to them it makes it that person's name for most purposes. Changing the name officially also requires only an affirmation or an oath at a court, although I don't think this would be the case here.
I think nobody would care much and the majority of politicians would go along with Count Binface as the proper way of address, because it'd be rude to do otherwise. Not the least because picking a fight with Count Binface would be seen as getting themselves dirty in non-serious politics. Not a very attractive proposition to be perceived as such for most political parties no matter how ridiculous their actions might be otherwise.