Use a big open room or the yard. Outside, you can set up safe obstacles with hay or straw bales, then spread out a pile of leaves for a finish line. Divide your partyers into two teams and mark a finish line about 20 yards off for big kids, closer for those under age seven. The first player on each team straps a set of legs around her waist so that two legs will dangle on each side of her when she's in the classic crab position. On "Go!" the first players scurry on all fours (well, eights), with their bellies to the sky, to the finish line and back. Each team then helps its player take off the spider legs before strapping them onto the next player, who "runs" the race and returns. This continues until the final player from each team comes across the finish line.