Making a solid summer comedy starring Jack Black, Michael Cera, David Cross and Hank Azaria should be so easy, a caveman could do it.
Somehow, despite the presence of those reliable actors and the highly advanced skills of comic veterans Harold Ramis and Judd Apatow behind the scenes, Year One manages to be a dud. A few amusing moments and ideas pop up here and there, but more often the script feels flat, with a needlessly heavy reliance on scatological gags. Black's character literally eats feces at one point, while Cera's urinates all over himself — upside down; it could be a metaphor for what everyone is stuck doing in this movie.
Black and Cera star as hunter Zed and gatherer Oh, mismatched Neanderthals who are banished from their village after Zed eats some forbidden fruit. Basically this allows Black to be Black (manic, unhinged but always overconfident) and Cera to be Cera (awkward, sarcastic but always sweet). Not much heavy lifting required of either of them.
Zed and Oh set off on a road trip that takes them from their primitive land to a series of biblical settings, including encounters with Cain and Abel (Cross and Paul Rudd) and Abraham and Isaac (Azaria and Christopher Mintz-Plasse). Ramis seems to be aiming for his own version of Mel Brooks' History of the World: Part 1, but there's nothing terribly memorable about these adventures.