Genk

Genk - an almost-game for public play vaguely reminiscent of something you almost remember. The authors explain "The most important thing is to look like you're really concentrating. There are no rules, just start playing and watch as people around you try to understand what the hell you're doing. It's even funnier if you've got someone at the table who isn't in on the joke."

Another "joke's on you" game of questionable taste, but of undeniably brief play value.

For a similar, but far more enlightenedly open-ended restaurant game, might I perhaps recommend Found Object Scrabble. You will not only look like you're concentrating, you'll be concentrating with all your symbolo-litero conceptual might.