Just like in Ghostbusters. And, fancy that, four real Ghostbusters herd them away. Sorta. Staged by the Improv Everywhere troupe in the same location as the Bill Murray-Dan Aykroyd paranormal classic, this is a pretty swell little prank.
Of course, this would've been a wee bit more impressive if the New York Public Library wasn't in on the gag, but the administrators — looking to remind people how awesome the NYPL is during these budget-crisis times — contacted the Improv Everywhere gang and gave them permission. Which, apparently, didn't extend to the security guard who stops the first ghost upon entering the Rose Main Reading Room. According to Improv Everywhere's behind-the-scenes account, the exchange went like this:
Guard: Sir, what are you doing?
Ghost: Um... haunting the library.
I do wish that the "Ghostbusters" didn't have inflatable proton accelerators, but this is still priceless.