Bobby and Castiel

Bobby Singer and Castiel having a working relationship as well as a mutual understanding. They both want to protect Sam and Dean. Although they don't work often together, Bobby and Castiel do protect each other. They first met when Dean and Bobby were going to summon Castiel, before they knew he was an angel. Although, Bobby is first to suspect Castiel of betrayal in Season 6. They become enemies for a while, but it doesn't last for long.

Background
The two first meet when Bobby and Dean summon Castiel to try and figure out who he is. When Castiel arrives, Bobby fires everything he has at Castiel, only to have Castiel keep walking towards him. Bobby is surprised to see Castiel unaffected, especially when Ruby's Knife doesn't work. When Cas gets near Dean Bobby attacks, only to be knocked out by Castiel. Castiel assures Dean there is no harm done. When first approaching the subject of angels, is willing to believe they exist. Later on as Bobby hears the stories about angels, his opinion isn't too high of them. It takes till Season 5 when they meet again.

Season 5
"Are you really gonna bitch to me? Quit pining for the varsity years and load the damn truck."

- Bobby When Castiel appears after he has lost his legs, Bobby demands Castiel heal him but Castiel can't due to being cut off from Heaven. The first major project Castiel and Bobby work on together is when everyone gets ready to hunt down Lucifer after receiving the Colt. Castiel stays at Bobby's place everyone gets ready there. Before leaving for the mission they take a group photo. During the mission Castiel wonders off, and this gives Bobby the hint of what's going on. After the hunt has failed, Castiel and the others return back to Bobby's.

The next time they work together in Point of No Return, when Dean attempts to say Yes to Michael. They work together to keep Dean and later Adam from leaving.

Bobby and Castiel start to develop a mutual understanding in Two Minutes to Midnight. Also a comic relief moment between the two when Bobby tells them about a storm about to wipe a city from the map. By now Bobby is in a wheelchair and Castiel has lost all his power. As they load the van, Castiel begins to feel sorry for himself and is feeling useless. Bobby gets angry and tells Castiel that it ain't bad, and not to preach to him about feeling useless. Bobby is still hurting from being in a wheelchair. Finishing off his speech to Cas, Bobby tells Castiel to shut up and load the truck.

So they set out to stop the shipment of Croatoan virus. Everyone does their part. Castiel finally figures out how to work a gun, and uses it to save Sam's life, which surprises Bobby. Once they have everyone out, they blow the building.

Then in Swan Song, they work together to help Sam gather demon blood so he can house Lucifer in his body without going on fire. As Sam leaves, Bobby and Castiel say their good byes, and watch his go. Both wish Sam to succeed, but they know there is a small chance of success. After Sam fails, both Castiel and Bobby lose hope. They both try to stop Dean when he wants to go after Sam, but Dean doesn't listen. As Dean leaves, Castiel and Bobby realize they need to help, as they exchange a look. So they go to the field where Lucifer and Michael are, and Castiel throws a holy oil bomb at Michael. Lucifer kills Castiel as a result, Bobby soon follows after desperately attacking the archangel.

Soon after the battle, God resurrects Castiel with all of his restored powers and additionally upgrades him. Castiel's second act upon revival (his first being to heal Dean) is to resurrect Bobby.

Season 6
"It was a bad idea letting them go." "Come on. You don't let Sam and Dean Winchester do squat, they do what they gotta, You know that. Anyway, we want Eve, we need coordinates. So we can sit here bellyaching or, we can poke that pig til it squeals."

- Castiel and Bobby Due to Castiel fighting a civil war in Heaven, Bobby doesn't see him as much as Sam and Dean do. Bobby does hear stories about Castiel from the boys though. But when they find a way to kill Eve, they call Castiel.

In Frontierland, Castiel sends the boys back in time. As Castiel leaves, he tells Bobby to pray for him in 24 hours so he can get Sam and Dean back. If its longer than that, Castiel would no longer be able to find them. Castiel later returns to Bobby's house injured and needing a safe place, and draws a sigil on Bobby's wall in his own blood. Soon as Castiel stands up, he passes out and Bobby manages to catch him.

With an hour remaining, Castiel wakes up and Bobby asks what happened. Castiel tells Bobby that Rachel betrayed him and continues on by saying that he will heal soon. Although Castiel tells Bobby that because of his weakened condition, he doesn't have enough power to bring Sam and Dean back. Bobby is shocked at the news, not to mention angry. Castiel tells Bobby that he could power up, he touches Bobby's soul. Castiel further explains that if he doesn't do it right, Bobby could explode. Knowing the risks, Bobby decides to trust Castiel and agrees to do it. So Castiel draws power from Bobby's soul and brings the boys back. This process does cause Bobby pain.

In Mommy Dearest, the hunt for Eve begins. When they have no leads on Eve, Bobby tells Dean to summon Castiel, since Castiel listens to Dean. When Castiel arrives he also reveals he can't find Eve. Once they do have the location they head out. Once there, Castiel discovers he is rendered powerless. When Sam and Dean leave to bring some orphans away, Castiel isn't too happy about. Bobby isn't impressed when Castiel begins to complain about it. Bobby tells Castiel no one can control the Winchesters, and they still need to find Eve. So they begin to torture the captured Jefferson Starship who's posing as the Sheriff in the town. When Bobby gets no results, Castiel steps in, and gets the answers. This triggers Bobby suspicions on what Castiel is really doing. After they have killed Eve, Bobby voices his concern about Castiel and believes that he is lying to them.

So they begin to investigate where Crowley is, but don't tell Castiel in The Man Who Would Be King. Bobby makes sure no one is telling Castiel what their doing. Unknown to Bobby, Castiel is spying on them, and kills any leads before they can trace it back to Crowley. Castiel even kills the demon counterpart of Bobby, Ellsworth. When they arrive they find the place clean, and Dean tries to convince Bobby that Castiel hasn't betrayed them, but Bobby sees no other way, and says:

"If there’s a snowball of a snowball’s chance here, that means we’re dealing with a Superman whose gone dark side. Which means we’ve got to be cautious, we’ve got to be smart, and maybe stock up on some Kryptonite."

- Bobby about Castiel

When they are attacked, Castiel saves them. They all thank Castiel for saving them and apologize for thinking that he had betrayed them. Then Castiel gives himself away when he says a version of the words Bobby had said before when Cas was spying on them. This gives them all evidence that Castiel has betrayed them. So they summon Castiel back to the house, and Bobby lights the holy fire ring around Castiel. Castiel's partnership with Crowley is now known.

In Let It Bleed, both Bobby and Castiel race against each other to find how Purgatory was first opened. Bobby seemed to lag behind Castiel a bit, until he saw the picture of the maid at H.P Lovecraft's party the night the portal opened. He figures out that it was Dr. Visyak, his old flame, and goes to protect her. Although she refuses his protection, and is eventually captured by Castiel.

Following that, In The Man Who Knew Too Much, any friendship or trust Bobby had for Castiel is gone when he finds Dr. Visyak in an alley, and he finds out that Castiel tortured her. Bobby tries to attack Castiel, but Dean stops him due to Cas being more powerful than Bobby. When Cas knocks down Sam's wal, its Bobby who wants to go after Castiel to stop him. Unfortunately, they are too late, and Castiel proclaims himself God. Making Castiel, himself an enemy to Bobby.

Season 7
"Well, he was friends with us, wasn’t he? You can’t get much dumber than that."

- Bobby about Castiel

Bobby was first to bow to Castiel, but due to the threat Castiel impossed on their lives. Bobby approaches Dean on how to deal with Castiel, but Dean has no plan. So Bobby doesn't pursue trying to find a way to stop Castiel. Then the idea to bind Death comes along, Bobby and the others head out. But that plan fails, when Castiel unbinds Death. Although Death tells them they need to get Castiel to let the souls go. Which Bobby doesn't think will happen.

Although Castiel later shows up on Sam's prayer asking for help. So Bobby helps Castiel and gets the portal ready. When its about to start, Bobby helps Castiel over to the portal. After Castiel lets the souls go, the Leviathans stayed in Castiel. With the vessel failing in Hello, Cruel World, they head to the water supply and Castiel disappears in the water. Bobby admits to being friends with Castiel, when they find his trenchcoat.

In There Will Be Blood, even though Castiel and Bobby haven't seen each other, Bobby knows Castiel is alive and suggests to ask Castiel for help.

Alternative Reality
In The End, it is shown that Castiel and Bobby both were in the resistance against Lucifer and defending people from the virus victims. Unfortunately, Bobby was killed in action, and Cas turned into a hippie.