Smashboards

FnaF used to be the talk of town back when I was in the 8th grade, everyone used to play, then everyone got hyped for the sequel, then everyone went back to doing their usual gig or two.

Regardless, if that happens, it'll be a major surprise. My safest bet is that if the series is ever going to get represented at all, then the least they could do is make a Spirit Board event or a "compensative" Mii costume a la Sans and Cuphead. Hell, I think Nintendo's actually liking this trend of "Mii costumes more hype than the actual character", so if any one of the Nintendo employees would find an interesting character from a relatively popular trendy game, then I think they can do it in a heartbeat.

Really? Sounds pretty dumb.

Also, Monika is on a PC-only game that's not an established series, so she's a really far shot in the dark regardless.

That being said, there is a rumor mentioned by Fatman about the most shocking Mii costume reveal in Smash history coming at some point, Freddy could plausibly fit that.

My personal theory about that "most shocking reveal" is a non-game Mii costume like Goku or SpongeBob - Miis were added as a response to those requests and Nintendo has done non-game crossovers before. (Shaun the Sheep in Mario Maker, Transformers in Splatoon, LOTS of product placement in Pikmin 2)