Year One starts off in the Stone Age as Zed (Black) and Oh (Cera) are basically the worst members of their tribe. The pair become outcasts and get thrown out into the wilderness when Zed decides to eat one of the golden fruits from the Tree of Knowledge and they start their pilgrimage across the lands (with a few time jumps that will ultimately lead them into ancient Sodom).
The first other humans the pair come across are Cain (David Cross, Arrested Development) and Abel (Paul Rudd, I Love You, Man). When the voyaging cavemen discover these brothers and bear witness to Cain's deed, they find themselves forced to go along with the murderer's outrageous story for fear of their own lives. But it isn't too long before Adam (Harold Ramis, Egon from Ghostbusters as well as Year One's Director) and the rest of their family learn the truth and end up running Cain (along with Zed and Oh) out of the village.
The trio travel a long way together and find themselves in a trading outpost where Zed and Oh recognize their love interests, Maya (June Raphael) for Zed and Eema (Juno Temple) for Oh, as well as Marlak (Matthew Willig), their tribe's biggest and strongest member. Unfortunately, the three former tribe mates are all getting ready to be sold as slaves. Needless to say, after some miscommunication, Zed and Oh end up in the same slave wagon as their friends.
Without going into too much detail and ruining more of the movie's plot for you, I'll just say that Zed and Oh's journeys take them not only to the home of Abraham (Hank Azaria) and Isaac (Christopher Mintz-Plasse, Superbad), but also into the city of Sodom, where a good third of the movie actually takes place. After reuniting with Maya and Eema, the focus of the story shifts from a pair of cave men wandering ancient Earth to the pair trying to free their romantic interests, but in Sodom, they will have to face strange rituals by the High Priest (Oliver Platt), power struggles between Princess Inanna (Olivia Wilde) and her step-father (Xander Berkeley), and just general Sodomy.
The DVD's special features include only a few basic additions. As you would expect from a comedy movie featuring this pair, there is a nice long gag reel as well as a slew of deleted and alternate scenes and an alternate-line reel as the actors try a little improv (which is actually the best extra in the bunch). There is also the obligatory making-of featurette that is pretty much what you would expect and nothing too special.
If you've read this far, then I don't have to tell you that the film is riddled with sacrilege. While I personally didn't find this insulting, there are many people out there who will undoubtedly find this film's use of Biblical characters and settings offensive, so I will warn you now, if you find yourself turned off by sacrilegious humor, then you will want to pass this movie up. That being said, most people will probably only want to see the film once anyway since the nature of the comedy doesn't really lend itself to multiple viewings and only skates above fart jokes most of the time (though it does dip that far on occasion). So if you are still interested in seeing Year One, then make it a rental.