A cop is sitting outside a local bar late on a Friday night, planning to nab a drunk driver.
As watches a crowd of people leaving he sees a guy fall out the bar door. ..then crawl over to the nearest car and starts trying every one of his keys in the door, when he realizes its not his car, stumbles to his feet and starts wandering towards the next car and starts trying his luck with that car.
After three wrong guesses the guy gets to his car, and opens the door and falls in his car. The cop is in awe when the man start the car and he sees the blinkers turning on and off while the brake lights are flashing repeatedly.
The cop gets out of his car and walks over to the car and asks the man to turn the car off and to step out. The man obliges and steps out of the car.
The cop checks his eyes, and they looked fine...so he had him walk a line, which the man did with no problem at all. Then he had the man recite the alphabet backwards and finally gave him a breathalyser which the man passes with a .00
The cop is really confused now and bluntly asks the guy, "Whats going on ?... I watched you stumble around, fall down, have trouble getting to your car, and you're completely sober !"
The man looks at the cop and says "Oh, Im the "Designated Driver" tonight."