Corny Birthday Puns

My brother's best friend isn't a dad yet, but he sure will be up there as a corny dad when he is... Years ago we went to Applebee's to celebrate my brother's 21st birthday. My brother's friend wasn't 21 yet. While they were standing at the bar, my brother orders a beer. Then his friend proceeds to do this:

Bartender- "What are you having?"

Brother's friend- "I'll have a beer....that'll be a root beer." ::winks at bartender and shoots his finger::

Bartender- ::SILENCE::