Enforced Method Acting: The infamous Times Square sequence was only shot twice, so as not to arouse the suspicion of tourists. Apart from Michael Keaton and a few extras that pass by close to his character, everything else around them is very real.
Moody, cynical, former drug addict Sam is quite different from Emma Stone's usual roles.
Reality Subtext: The film is a clear analogy for Michael Keaton's struggles with escaping his I Am Not Spock status as the man who played Batman in the first two entries in the 1989 film series. The premise itself, in which an actor attempts to escape his typecasting as the titular superhero by taking the lead in a play, is an almost note-for-note calling card for Keaton's attempts at escaping the mantle of the Caped Crusader.
Starring a Star as a Star: Famous actor Michael Keaton (well-known for having twice played Batman in the 90s) portrays Riggan Thomson, a famous actor well-known for having twice played in-universe superhero Birdman).
The first sound heard in the film is score drummer/composer Antonío Sanchez asking director Alejandro González Iñárritu a question in Spanish, and then detuning his drums as desired by the director, who was sitting in on the sessions and helping to direct the score. Iñárritu can also be heard in the background of the closing credits.
Zack Galifinakis was praised for being especially skilled at improvising whenever he messed up during the film's long takes, saving everyone from having to start over.
Unintentional Period Piece: Inverted to intentionally become a period piece. There are references to the MCU, as Birdman was released at a time when superhero films were at the peak of their popularity and this partially comes across as a response to that.
The movie was originally going to have a different ending - right after Riggan pulls the trigger on stage, the scene would have cut to him sitting in front of either James Lipton or Charlie Rose, who would tell him that his play was getting good reviews, before moving to a dressing room occupied by Johnny Depp, who would be sitting next to a poster of Captain Jack Sparrow, which would come to life and ask Depp "What the fuck are we doing here, mate?"