The Sean Mulligan Effect
When someone you know, knows someone else you know, but they don't know that you know each other until you mention the mutual friends name 'Sean Mulligan' - to which the reply is usually "Oh yeah, I know him. He knows everyone!"
A: So how did you meet Andrew?
B: Through a work colleague, thanks to the Sean Mulligan effect.
B: Through a work colleague, thanks to the Sean Mulligan effect.