"Clever Plan" joke

A regular walks into a bar, looking blue. The bartender starts setting him up his usual, and our man, Dave, says, "No, no - just a glass of milk."
Taken aback, the bartender asks what the hell has gotten into him?
Dave responds, "Well, my wife told me that if she catches me coming home late and drunk after I've thrown up on myself one more time, she'll divorce me! And this time she means it. I'm blue..."
"Hey, no problem!" the bartender says as he starts setting Dave up again. "Do you have any big bills on you?"
"Well, sure," says Dave. "I just got paid."
"Okay," says the bartender, "drink all you want and rolf like you usually do, and when you get home and she bitches, show her a $50 bill and tell her someone threw up on YOU, then offered to pay for the shirt!"
What a great idea, Dave thinks, and starts knocking them back.
Later that night, when Dave gets home late, drunk, and having thrown up on himself, his wife meets him at the door, screaming: "Damn it, Dave - I've told you! That's it!"
"Wait! Wait! It's not me! Some drunk threw up on ME and gave me this $50 bill to pay for my shirt!"
She yanks the money out of his hand. "Dave, this is a $100 bill."
"Well," Dave replies, "that same drunk shit my pants as well."