So in my opinion I think Funtime  Foxy is either a transgender female to male or gender fluid. The reason for this is because Funtime  Foxy talks like a boy but can be found in ladies night 3 if I remember correctly. The reason why this can be used to say they are trans is because it is possible that on the ladies night they are in it is one where the trans female to male animatronic has to participate. Why you may ask well maybe not every animatronic accepts that Funtime  Foxy is trans so as a compromise they decided that on one night Funtime Foxy has to be with the girls. Or it could also be to torment the character in custom night. Maybe they are trans phobic so in order to make him suffer more with Funtime  Foxy being trans they make Funtime Foxy be with the girls one night. Now the reason they could be gender fluid is because it is possible that the one ladies night Funtime Foxy is in they feel like a girl so they are with the ladies on that night to make them feel happier. So that's my theory for now at least maybe Scott will eventually stop making people confused about Funtime Foxy's gender but until then we can make theories about it.