That thing with the big opening

I was waiting in Christopher's room for him to finish brushing his teeth so we can read and I hear him call out of the bathroom, "Mom, I filled that thing up all the way in bathroom.  Come see it."  Being lazy, I tell him to just tell me what it is.  He says, "It's that snowman face thing that has the big hole in the top of it."  Huh?  As I rack my brain to figure out what I Christmas type thing I put in his bathroom.  Oh yeah, most people call those things cups...