WooHooium is a type of metal that was added in The Sims 3: Ambitions expansion pack. It can be obtained by mining, sculpting, digging through trash, getting pet to dig in dirt, and exploring catacomb.
Although little is known about it at the moment, it is said that taking a WooHooium ingot and putting it on either side of a double bed means that no WooHoo will ever be rejected. Little hearts appear from the ingots when the WooHoo is in progress. This metal looks different from other metals; WooHooium has a heart on it in the space (on the ingot itself) where most metals in The Sims 3 have a PlumbBob.
Perhaps the easiest way to obtain WooHooium is to lose the stone sculpture: however, it is very random as it relies on the premise that the stone breaks, and even if it did, WooHooium is one of the many items competing.