Don't do that in front of bartenders

I think you mean always do it in front of bartenders.

Congratulations, you played yourself.

"Don't do that in front of bartenders."
How about you don't do that at all....?....

Good guy bartender!!

That's a nice thing to do

One tiny remark: I think the next girl this guy uses that trick on would've greatly appreciated if instead of doing a funny drink switching prank you'd put the laced drink behind the bar as evidence and called the police. Just sayin ...