In some places (including much of the US, I believe), you can be arrested for drunk driving even if you're not in the driver's seat. Here's some info on California's laws [1].
The idea is that you are in the car and capable of driving it, even if you're not in the driver's seat yet. According to the urban legend, the trick is to get rid of your keys if you need to sleep in the car while drunk (i.e., swap keys with a friend who's in a different car), since you can then argue that you did not have the ability to drive the car.
Germany seems to be more lax. When I started to drive I got this advice: Always keep a half-empty bottle of vodka (or anything) in your trunk. If you have an accident while driving drunken. Get the bottle before the police arrives. Tell them: That accident was such a shock, I had drink something.
Disclaimer: I'm not a lawyer. I never tested this. Do NOT drive drunken!
The idea is that you are in the car and capable of driving it, even if you're not in the driver's seat yet. According to the urban legend, the trick is to get rid of your keys if you need to sleep in the car while drunk (i.e., swap keys with a friend who's in a different car), since you can then argue that you did not have the ability to drive the car.
[1] http://www.rencherlawgroup.com/Practice-Areas/DUI-Defense/Pa...