Let's Go to Prison

John Lyshitski (Dax Shepard) has spent most of his life in prison, serving three different sentences. Each of his three trials were before Judge Nelson Biederman III, who habitually imposed resentfully tough sentences. After being released from his third sentence, John decides to take revenge on Biederman. John tries to determine when Biederman will be presiding over his next case, only to discover that Biederman died three days before John's release.
He turns his attention to the judge's brash son, Nelson Biederman IV (Will Arnett). At a dedication ceremony for Nelson III, John breaks into Nelson's BMW, wrecks the interior of it and empties Nelson's emergency inhaler. After the ceremony, Nelson drives off and, finding his inhaler empty, panics and hyperventilates. He stops at a pharmacy and frantically searches through the shelves, desperately seeking a replacement for the empty inhaler, which he finds and immediately opens to use. The pharmacy owners think he's a junkie seeking a fix. One owner mistakes the inhaler for a tiny pistol and calls the police.
Nelson is arrested and charged with assault and armed robbery. He demands that the Biederman Foundation do everything possible to have him acquitted. The board nearly complies with Nelson's demands, but, as they are fed up of him and his behaviour, they see an opportunity to be rid of him. They get him a terrible defense lawyer for the trial. Nelson is found guilty and sentenced to three to five years. John, not satisfied with Nelson merely going to prison, decides to join him in prison by committing a crime. At his trial before the same judge Nelson had, John pleads guilty and asks for the same sentence (3â5 years) at the same prison that Nelson is in. He manages to become Nelsonâs cellmate, pretends to be his friend, and gives Nelson wrong advice on surviving life in prison.
Nelson gets himself out of the many situations that John's misinformation creates. He meets gang leader Barry (Chi McBride), an imposing, brawny gay fellow who engages Nelson into a relationship. Despite his intimidating appearance, Barry is a sensitive romantic â he likes smooth jazz, he supplies potential romantic partners with his finest toilet-made Merlot, and he has transformed his prison cell into a candle-lit, rose-bedecked passion parlour. Nelson first submits to being his partner out of fear, but then he genuinely grows fond of Barry and is happy in the relationship.
Nelson reaches his one-year parole hearing not only relatively unharmed, but the "top dog" in the prison hierarchy. However, John will not allow his target to escape prison so easily. He manages to get Nelson's parole denied. Enraged, Nelson confronts John who then confesses to putting Nelson in jail. The two get into a fight. John quickly realizes that he is now Nelson's target. The guards set up a death match between the two. However, John and Nelson secretly hatch a plan to inject each other with a coma-inducing drug. The guards and prisoners, believing that they are dead, bury the pair in the graveyard. Nelson has given Barry access to funds, to bribe the mortician to avoid an autopsy. Barry later digs up the two. John, Nelson and Barry begin a new chapter of life, starting a winery (the product being "toilet wine"). The film ends with Nelson, Barry, and John now the best of friends, happily living free life in society.

Question: Who becomes Nelson's cellmate while he is in prison?
Answer: John