
This one really should be true. Alcohol is a depressant; caffeine is a stimulant. They should cancel each other out.
But they don't. The only "drunk" trait coffee can counteract is the tired, foggy feeling. So drinking coffee when you're drunk just makes you a judgment-impaired, over-confident, dehydrated, uncoordinated and very awake drunk person [source: Discovery].
Which would probably be fine except that adding "very awake" into the equation can make a drunk person feel less drunk -- thus making driving a car, operating a backhoe or chopping some vegetables seem like perfectly reasonable propositions.
The effects of alcohol fade as it's eliminated from your system, which happens at a rate of about one drink per hour, coffee or no coffee [sources: Freudenrich, Discovery].
Next, a happy one!