The bartender asks him "What'll you have?". The guy answers, 
"A scotch, please". The bartender hands him the drink, and 
says "That'll be five dollars", to which he replies "What are 
you talking about? I don't owe you anything for this".

A lawyer, sitting nearby and overhearing the conversation, 
then says to the bartender, "You know, he's got you there. In 
the original offer, which consitutes a binding contract upon 
acceptance, there was no stipulation of remuneration". The 
bartender's not impressed, but says to the guy, "Okay, you 
beat me for a drink. But don't ever let me catch you in here 
again".

The next day, same guy walks into the bar. Bartender says, 
"What the hell are you doing in here? I can't believe you've 
got the audacity to come back!". 

The guy says "What are you talking about? I've never been in 
this place in my life", to which the bartender replies "I'm 
very sorry, but this is uncanny. You must have a double."

To which the guy replies "Thank you! Make it a scotch."