Bobby grew up with an abusive father, who Bobby shot and killed when he was a teenager while protecting his mother. Bobby buried his father in the salvage yard.
A mechanic by trade, Bobby became a hunter after he had to kill his wife Karen Singer when she was possessed by a demon. Rufus Turner is the hunter who exorcised the demon and helped cover up Karen's death. It was Rufus who introduced Bobby to the world of the supernatural, and they hunted together for many years until a hunt went wrong in Omaha around 1993. They become estranged after this although they had contact and some reconciliation from 2008 until Rufus' death in 2011.
Bobby's guilt over Karen's death causes her to inhabit his dreams. She is later resurrected by Death and turns into a zombie and he has to kill her again, which causes him more grief.
Bobby has known the Winchesters since at least 1991 - he gave an eight year old Sam an amulet as a Xmas present for his father, which he eventually gave to Dean. Bobby also played catch with Dean, and took the brothers deer hunting. John Winchester and Bobby were not necessarily on good terms - Dean comments that the last time Bobby saw John he nearly "filled him with buckshot". It is to Bobby's place that Sam and Dean go to grieve after John's death. After this Bobby's relationship with the Winchesters grows even closer, and he becomes both father figure and friend.
Bobby sells his soul to Crowley in exchange for information on Death's location. Crowley also makes it possible for Bobby to walk again. He says that he will return Bobby's soul after Lucifer is defeated. It is later revealed that Bobby was given the standard ten years to live until his soul is dragged to hell. Bobby is able to trick Crowley and negotiate the return of his soul.
Bobby is the first one to voice concerns about Castiel's activities, and is with Sam and Dean when Godstiel appears. He helps to send the souls back to Purgatory, and tries to keep Sam and Dean grounded in the aftermath of losing Castiel, Sam's hallucinations, and the appearance of the Leviathans.
After being shot by Dick Roman, the leader of the Leviathans, Bobby lapses into a coma and dies. His last word is an affectionate "Idjits" to Sam and Dean. However, Bobby refuses to go with his reaper, remaining on earth as a spirit to help the Winchesters, when he is able. However, after becoming a Vengeful Spirit temporarily, he asked Sam and Dean to put him to rest, which they did. His last request was for them not to give into vengeance like he did and when their time came, to move on.
Dean Winchester [Surrogate Son/Comrade]
Sam Winchester [Surrogate Son/Comrade]
Bobby is like a Men of Letters, only without the official title. He collects books and reads them. He's like a Demonology Encyclopedia, only with legs and a heartbeat.
Bobby is a good mechanic, and can build a car from the ground up.
He likes his whiskey. Or any alcohol, really. He's a surly alcoholic.
He has an affinity for dry wit, sarcastic humor and taunting Crowley.
