Threesome

Olivia: Vanessa, you're in love with Dan, and everybody here knows it.
Dan: Olivia that's crazy...c'mon...
Olivia: Ok... I don't need any opinion on this. I quit.
Vanessa: Oh no you don't! I quit!
Blair: What is going on? Are you both been having a threesome or something?
(Dan turns around)
Blair: Oh God! How stupid can you be? The third person is always supossed to be a stranger!
Dan: Blair... this is my mess, i'm gonna go talk with the girls.
Blair: In which order?
(Some say "three's a crowd". My question is: is it?)