Cinema buffs love an on-paper weird casting that turns out to be genius. Quentin Tarantino has the knack for it - Travolta was nowhere, literally nowhere, when cast in Pulp Fiction and Kurt Russell was probably the only actor on the planet who could have pulled off Death Proof, despite his preceding credits reading Dreamer: Inspired By A True Story, Poseidon and family-comedy Sky High.

Michael KeatonMichael Keaton stars as RIggan in 'Birdman'

When Alejandro Inarritu - the man behind Babel, 21 Grams and Biutiful - recruited Michael Keaton for his avant-garde new movie Birdman, eyebrows were raised. Though an incredibly talented actor  and once regarded as one of the most in-demand on the planet, Keaton hasn't delivered a stand-out lead performance since Live From Baghdad, some 12 years ago.

More: 'Birdman' is serious contender for Oscars' Best Picture

As it turns out, Birdman is one of the best reviewed movies of the year and Keaton's performance as an ageing actor struggling to mount a Broadway play has seen him installed as favourite to win Best Actor at the Oscars.

Speaking to Indiewire about how the collaboration came about, the 63-year-old explained, "I was working on a movie in Toronto and I got a call saying Alejandro wanted to meet.I had seen, I think, everything he had done and thought, 'Man, these are the kind of guys you want to be in business with.' I called back the next day and figured out a way to make it work. We had dinner together, had a fair amount of wine. The script would have had to be horrible for me to say no."

BirdmanMichael Keaton [L] stars opposite Edward Norton [R] in 'Birdman'

In Birdman, Keaton's character Riggan is a washed-up star known for once playing an iconic superhero. It doesn't take a movie expert to spot the correlation here.

"There was that moment when I was like, 'Is there going to be an issue in terms of having played Batman?" said Keaton, "Maybe Alejandro remembers it differently, but there was no time to discuss this. There was so much work to do. I always say about this movie: If we finished and people said 'It was pretty good,' I would have been fine with that. Turns out it's my most favorite venture not only in movies, but in life that I've gone through."

More: Venice Film Festival: so 'Birdman' just joined the Oscars race. Big Time. 

"Led by a fantastic Michael Keaton, Birdman is a deeply thoughtful and darkly hilarious meta dissection of egotism that satirizes the entertainment business with a compelling visual style that is all its own," wrote Zachary Shevich of We Got This Covered in his review of Birdman.

Birdman gets a limited U.S. release on Friday (October 17, 2014).

Watch the trailer for 'Birdman':