As a Potterhead, this is by far the best exchange I have ever witnessed in a Barnes and Noble. 

• Me: *le looking at the merchandise at the Harry Potter table*
• Old guy: *le walks up and flips through a poster book*
• Girl: *walks up* Dad.. What are you looking at? What's.. Harry .. Porter? 
• Guy:   Please. Just stop.
• Girl: What?
• Guy: *sighs* Harry Potter is literally the greatest phenomenon of your generation. There are books and movies and it's in the media all the time. It's basically imbedded into our culture. You can't go a day without hearing about it. Especially now. Stop trying to act cool.  I know you know what Harry Potter is. If you're trying to impress this girl,- *gestures toward me* - you're failing.This girl here probably thinks you're a stuck up teenager. For gods sake, I'm pretty sure she's contemplating buying a wand.
• Girl:  *blushing* Whatever. Can we go now?
• Guy:  *rolls eyes* Yeah.
• Girl: *walks away*
• Me: Muggles.
• Guy: Tell me about it.