Riggan hears a deep voice talking to him. The voice is coming from inside of his head and is telling him that he could have had it all.
This is the voice of Birdman, the character he used to play. He's berating Riggan for giving up a life of stardom and money and fame to become a nobody director.
Riggan tries deep breathing but it doesn't help the voice go away.
So instead he uses his telekinetic powers to smash Sam's vase of flowers against the wall.
In the next moment he's in the middle of a media interview where he's being questioned by a tabloid woman wondering about the pig semen he may or may not inject for its facial rejuvenating properties, a theater critic who suggests the play is an attempt to not be a washed up movie star, and a Chinese reporter who's really excited by the idea of a new Birdman movie.
Jake comes in and these people go away. Jake has the Ralph situation under control but now they're stressing about finding an actor.
Lesley, one of the actresses, comes in and says her lover Mike, a famous theater actor, wants to do it. Everyone's excited.