Similar to hot potato or time bomb, all the boys stand in a circle. One boy is handed a water balloon, a real egg, or something else round. The music starts and the balloon/egg (a.k.a. dinosaur egg) is passed to the next boy. No one wants to be left with the dinosaur egg, because that boy is out of the game. Continue playing until there is only one boy left.
References / Source:
Circle Ten Council