It may (or may not) be a hoax.
"Justin Long: This set had the best prank I've ever seen pulled. I wasn't a part of it. It was pulled on me by Luiz Guzman. The whole cast was in this bathroom, waiting to do a scene. It was kind of late at night. And Luiz had been shooting for a couple of days. We didn't have a good beat on him. We didn't really know what he was about. He was this respected actor. We were all kind of nervous to be around him. He'd been weird with the director all day. There was this weird drama in the air. Then, all of a sudden, he goes, "No, I'm going to say the line the way I want to do it." And the director was like, "Can we just say my line, and then we can do another take, and you can say what you're going to say?" He's like, "If we do that, then I know you're not going to let me do my thing, so **** no. I'm going to say my ****ing line and that's the way it's going to ****ing be." The director goes, "Please..." And Luiz goes, "Bitch, get your ****ing hand off me. I will ****ing slap you upside the head." And we were all frozen. They have it all on tape. No one knew. Luiz was going off. He was like, "I'll fight you, bitch. I work with Paul Thomas Anderson." He started naming people, "I worked with the best. Who are you, you first time piece of ****? I will bitch slap you upside your head." Rob, the director, was shaking. I thought he **** in his pants. Luiz stormed out of the bathroom. There was just that tension in the air. We thought there was going to be a fight. But then he comes back in about a minute later and goes, "April Fools day, bitches!" It was the greatest. He got everybody. And the director was in on it. "
Justin Long Interview
"How do you like THAT 'misanthropic panache,' Mr. Goldstone?" - PalJoey