Robert De Niro needs no introduction. He has played Vito Corleone, Travis Bickle, Jake La Motta, Al Capone, Rupert Pupkin...even Frankenstein’s monster! He has been a gangster, a policeman, a priest, a saxophonist, a comedian, and a magician. But above all, he is a true legend, a winner of two Oscars, and the idol and aspiration of many generations of actors.

But for the past few years, there has been something growing inside of him, something that has finally superseded his skills as an actor. It is a recurrent gesture, a grimace that emerges as if with a life of its own. Coinciding with De Niro's birthday, here is our diagnosis: He suffers from...Robert De Niro syndrome!

We love getting into the nitty-gritty of what makes our favorite actors tick! Check out our recent videos on the careers of Michelle Yeoh, Ewan Mcgregor, Philip Seymour Hoffman, and Robin Williams.