Jimmy Fallon -- The Breast Book Signing Ever

Jimmy Fallon got two big eyefuls at a signing for his new book "Thank You Notes 2," when a fake mustached fame-hungry female "fan" went topless at a Barnes and Noble in Manhattan on Thursday.

Turns out the streaker is this chick named Holly Van Voast, who has been known to get attention by flashing her lady goods in public before. Just a few months ago, the peroxide blonde was arrested for baring her knockers inside NYC's famed St. Patrick's Cathedral.