Second Pick Friend

That one friend who you only hang out with when everyone else in the friend group is taken and you have no one else to partner up/hang out with. Usually tends to be someone who's half funny and a little bit interesting with a single quirk that allows them to be in your friend group.

Bob: Hey Joe, wanna partner for gym class?
Joe: Nah, I'm with Rick.
Bob: Alright how about you Deb?
Deb: I'm with Alan, sorry. Guess you'll have to partner with our Second Pick Friend, Zack
Bob: Ah shit.