Can male actors play little girls?

For instance, Robert de Niro. He went on an eating tour in the south of France to gain 60-pounds for “Raging Bull” (1980) and wearing custom-made silk underwear in order to be like Al Capone in “The Untouchables” (1987). Because of such close attention paid to small details, he’s considered one of the hardest working actors in the multiverse. But what if he had to play the part of a little girl?