If it were built around Keaton
alone, Birdman
would be
strong enough, but Iñárritu draws a clutch of stellar turns from Andrea Riseborough (as the leading lady Thomson may or may not
have got pregnant), Zach Galifianakis (in subtle, restrained mode as Thomson's loyal producer) and Amy Ryan (as Thomson's estranged wife, a
voice of calm reason in a topsy - turvy world).