Few things in this world are guaranteed: death, taxes and bounce houses at kids' birthday parties. Immortality and offshore accounts? Can't help you there. But breaking free of those expensive, inflated vinyl cells and doing something original and super fun on your wee one's special day is just a few bucks away. All you need are a couple drugstore wading pools and cans of shaving cream from the 99 Cents Only Store -- one can per kid is ample. Fill the pools with water and let everybody get wet. Then the birthday kid starts spraying and the rest of the party joins in (and if any gets into a partyer's eye, just wash it out). The more shaving cream, the slipperier it gets, but what's a birthday party without a few tears? After an hour or so, everybody goes home exhausted and smelling chemical-clean. And if the weather's not conducive to pool play, get cheap rolls of toilet paper, pair off the kids and play "Mummy" - one kid wraps another from head to toe.