Wild Wasteland

 is a trait which only appears in Fallout: New Vegas and adds various 'wacky' content, as well as modifies existing content and special encounters.

In an interview with Chris Avellone, he notes that the Wild Wasteland trait may add more references to older content in Fallout and Fallout 2, in regards to special encounters. Players without Wild Wasteland will find less silly analogues in places where Wild Wasteland modifies things.