Board Thread:General Discussion/@comment-24973452-20160905181416/@comment-28662609-20170528212749

"They" should be used. It has always been used for hundreds of years where gender is unknown/too complex to go over and is very clear.

I thought that Mettaton was trying to say "hold on" or something similar personally. Accidentally misgendering someone is not something this game goes into (quite thankfully).

As for Mettaton, I believe that he was "they" when a ghost. It'd make sense.