The Ghostbusters are a group of nerds that became cool when they started fighting ghosts (but they're still nerds). The Ghostbusters are not trained or authorized in any way to do what they do, but the EPA is a bunch of losers and they can't do anything about it. The Ghostbusters are primarily active in New York City, Possum City, and South Korea (on Mondays).
The Ghostbusters are infamous for their ability to capture any ghost, anywhere, at any time. In fact, the only ghost to date that they have never caught was Casper, And Luna but Casper is a stupid little brat, so we don't care about it. The Ghostbusters were at one point so famous that Wario challenged them to a duel in the 9th Dimension. The Ghostbusters accepted and won by using Wario's fat against him. They keep trying to catch a ghost named Luna. but Bjorn will won't let them.