Their interruption usually ends the conversation you and the person of the opposite gender were having.
Jill: I thought it was good too. I'd watch it again.
Tim: That's good. A movie for home, then. So, I was wondering if you wanted to do something tomorrow?
Jill: Oh! I'd --
Steve: Hey you guys, what did you think of the movie?
Jill: Hey Steve. Tim and I were just talking about it, we both thought it was good.
Steve: That's cool. Well, I'm going to go get some coffee.
Jill: What were we talking about?
Tim: Oh, nothing.
Tim: Man, Steve is such a talkblocker.