Assembled are the usual band of freaks and geeks. The aliens the critters the mutants or just the fanboys who have knowledge of the paranormal - and more. They make up the Bureau of Paranormal Research and Defense, they protect a world that generally have little idea they exist. As founder Professor Trevor Bruttenholm once said, when things go bump in the night, the BPRD bumps back.
The Bureau is a multifandom agency RPG. Any characters from sci-fi/fantasy fandoms can be played, and you do not need to have a knowledge of the Hellboy universe.