Usually referred to as a black person. When used you are asking who let you out of your cage at the zoo.
Hey Curtis who let you out ? How'd this one get out?
by Chimp you out February 3, 2016
usually a term used when your friend tells you this crazy story about what he did you automatcilly have to call him a maniac or psycopath and then you have to tell them "who let you out of the asylum!?"
Haro: so i was fuckin blown right now and then i didn't know who Tobar was

Andrew: Damn! foo you a maniac, Who let you out of the Asylum!?
by El Equis June 6, 2009