Must be a Special Encounter courtesy of the Wild Wasteland trait á la F3's Firelance Encounter
i love that trait... i will never be able to play without it.
Its similar to how "explorer" worked in fallout 1 and 2, just to name a few random encounters.
montypython and the holy grail (2 encounters)
-the bridge of death
-a group of brotherhood knights looking for the holy hand grenade.
dr.who's time machine/police box.
in fallout tactics you could run into the actual cartoon vault boy and have him join your party