Robert Di Niro is the 1970′s is my second favorite actor (Al Pacino in the 1970′s being my number one). He’s known for his method acting and meticulous preparation for roles. For Taxi Driver, he went so far as to obtain a taxi license and actually work as a cabby in New York City for a few weeks.
Retronaut featured his actual license, which I’ve stolen and posted above.
Now whether or not he practiced killing pimps before the shoot, we may never know.