I've been searching for nicknames for Kamui on the Web and found the following:
Kobay-crashi (from GP2)
Gandalf - after Valencia 2010
The majority are obviously based on his name and nationality, and of course there are two which have links to the fact that if he hadn't gotten a race seat in 2010 he was going back to help out in his dad's Sushi restaurant - strange for a guy who doesn't go for the "raw fish" sushi options.
But the funniest thing I've heard is that he wanted to be a stand-up comedian before deciding to race, so, in the spirit of F1 there's only one practical joker from the grid to whom he can be compared.
Kamui - I bestow upon you the nickname "Berger". I hope you keep up his tradition of practical jokes carried out on your fellow "unsuspecting" drivers - particularly those that you'll be fighting wheel-to-wheel in the following GP.
I'm thinking of making this one stick in the same way I have a tendency to refer to Alonso as Nadgers (that one for no particular [McLaren] reason!).
All hail Berger Kobayashi.