taking the juice for free 

To fake one's qualifications for a particular discussion by pretending to know what the other person is talking about (often out of politeness or fear of admitting that one doesn't get a reference), and then to continue enjoying the benefits of the discussion (including unearned enthusiasm from the other person, who thinks he/she are talking to someone who has something in common with them).

Example #1:
Person 1: So how about them Bruins?
Person 2 (not knowing anything about hockey or the Bruins): yeah..
Person 1 (now excited): YOU SAW THE GAME? It was so good!! I missed the last 15 minutes though!!
Person 2 (now deep in a lie): Err, yeah. They did great.

Person 2 didn't earn person 1's enthusiasm (energy/"juice"). They were taking the juice for free.

Example #2:
Person 1 (pointing at the moon): "That's no moon. It's a space station!"
Persons 2 and 3 get the reference and laugh
Person 4 (who never saw Star Wars, doesn't get the reference, can TELL it's a reference of some kind, but doesn't want to admit to not knowing the reference, weakly smiles or fake laughs): Ah
Person 1 (suspicious): Are you taking the juice for free?
Person 4 (caught): Yeah I have no idea what you were talking about

taking the juice for free by jkeegan January 8, 2014