I've never had an official name for the male character off-camera. I've just been calling him Guy in the scripts, but that's more just a designation than his name. So if you want to suggest some possibilities for the name of "The Guy", send them my way and I'll throw up a poll in a week or so to let you all pick his official name.
---Script---
Jess:
"Oh yeah?"
"How hot do you think I look?"
Guy:
"Turn around again so I can get a second look from the back."
"Definitely a 6 or 7."
Jess:
"What?"
"Only a 7?"
Guy:
"That ass is a 9 or 10, for sure."
"But it's kind of putting your front to shame."