"Hey, the Big M! How's it hanging, McFly?"
Needles to Marty McFly

"How's it hanging?" was an expression used in 1985, meaning "How are things going with you?".

The phrase was a double entendre, and depending on the intonation, could be a sincere greeting or a form of contempt toward the addressee. Douglas J. Needles was still using this as a conversation starter thirty years later in 2015.

In both 1985 and 2015, Needles' use of the greeting was insincere and part of his own manipulative behavior.