Really?

I highly doubt Papyrus' mom is capable of selling hotdogs, what with the whole 'only you and papyrus and gaster (and maybe sans) remember she exists' thing, but okay.

what if rever guy a boi then they would be gay

The River Person is a female.
The River Person being Papyrus' mother is the only logical explanation for the River Person's being.

then who said they liked the Other?

Well simple, it was [redacted].