The "if there isn't a god/invisible pink unicorn/giant inflatable Mrs Ross bent on destroying the union [delete as appropriate], it doesn't make a difference to you whether you belived in them when you die, but if there is and you don't believe in said deity, you're in deep shit and will burn in hell" thing is Pascal's Wager (roughly paraphrased, of course
). The guy in question was Blaise Pascal. Can't remember much else about him. I think he was French.
Unfortunately, the argument has a few problems. For one thing, it ignores the existence of many different belief systems, assuming automatically that only the christian belief system exists. However, if I died believing in a pink unicorn and discovered Mrs Ross was in fact in charge, (and you thought that was a bouncy castle in venue 1 last night!) I'd still be screwed, and instead of sitting until the small hours messing about on computers, I would have spent my life trying to believe a load of crap and getting my head around the apparently non-contradictory nature of something being both invisible and pink, for no reason whatsoever.
Even if the IPU existed I'm sure it wouldn't be all that impressed with me anyway if it was aware I'd only gone along with its evil plans for world domination out of fear of being roasted on a spit. And if it was unfriendly enough to condemn billions of reasonably good people to eternal torment just over a small mistake on their part (such as being swayed by the followers of the giant Mrs Ross handing out doubtlessly classy and well-produced flyers) then I personally wouldn't rate it too highly on the sanity and stability stakes, and wouldn't count too much on my hopes of it not going into a mood and just sending me off on a whim to join the majority of all the other people who had ever lived. (Including just about all my friends, come to think of it...)
(Thus ends the sleep deprived ramblings of an English student trying to avoid an apparent eternity of studying Hugh McDiarmid's poetry before her seminar tomorrow...)