<P> Castiel / ˌkæstiˈɛl / is a fictional character portrayed by Misha Collins on the CW Television Network's American television series Supernatural . An Angel of the Lord, he first appears in the fourth season, and is used to introduce the theme of Christian theology to the series . In the series, Castiel brings Dean Winchester back from Hell and frequently helps him and his brother Sam in their battles with various demons and angels along the way . During his travels with the Winchesters, Castiel develops friendships with both men . As an angel, he possesses a number of supernatural abilities, including the ability to kill demons . Initially, the character demonstrates complete devotion to God and little emotion . However, his interactions and experiences with Dean Winchester and Sam Winchester, as well as certain revelations about God and his fellow angels, have a humanizing effect on him . This, despite the stress and harm it causes his character, allows him to develop an independent will as the series progresses and helps the show address topics related to free will . </P> <P> Unlike the stereotypical portrayal of television angels, Castiel does not always help people, and is willing to kill innocents if needed . Collins originally read for the part of a demon, as series creator Eric Kripke did not want fans to find out that angels were being introduced to the series . Collins prepared for the role by reading the Book of Revelation, and based his portrayal on his younger brother . Critics and fans have responded highly favorably to the character . In response, the show's creators expanded his role in the series, upgrading him to a main cast member in the fifth and sixth seasons . After being a special guest star in the seventh and eighth seasons, Collins was upgraded once again to regular cast member status for the ninth, tenth and eleventh seasons . </P> <P> At the end of the third season of Supernatural, main character Dean Winchester is in Hell after being killed by the hellhounds of the demonic antagonist Lilith . In the season four premiere "Lazarus Rising", the angel Castiel is introduced as the one who brought Dean back from Hell and resurrected him . Because merely perceiving his actual form typically results in blindness, he takes a human host--James "Jimmy" Novak, a "devout man" who prayed for it--to communicate with Dean, and tells him that he has been brought back because God has work for him . Lilith is breaking the 66 seals in order to free Lucifer, and Dean must stop her . </P> <P> Castiel continues to appear throughout the season, at one point sending Dean back in time and later tasking him and his brother Sam with stopping witches from breaking another seal . He returns with fellow angel Uriel at the end of the episode "I Know What You Did Last Summer", seeking to kill Anna Milton, a fallen angel with the ability to "hear" the communications between angels . In the following episode, "Heaven and Hell", Anna uses an ancient Enochian sigil to send the angels away, though they manage to track them down later . Once there, Castiel expresses regret at having to kill Anna . Before they can carry out their duty, however, they are confronted by the demon Alastair and two of his minions . A fight ensues, and Castiel is nearly defeated in the battle by Alastair . He is saved by Dean, and they in turn are rescued when Anna regains her powers . Although Uriel nearly vents his frustration on Dean, Castiel stops him, and the two leave . Castiel later becomes suspicious of Uriel and confronts him in "On the Head of a Pin". Uriel admits he and certain other angels are now working together to free Lucifer, having grown weary of never hearing from God and jealous of His favoritism for humanity . He asks Castiel to join him, but Castiel refuses and attacks him . Uriel eventually overpowers Castiel, but is killed by Anna before he can strike the finishing blow . During this time, the orders he is getting from Heaven of questionable morality and the influence of Anna cause him to start to have doubts about Heaven's plans . He later returns in "The Monster At the End of This Book" to explain Chuck's role as a Prophet and later when Dean calls him to help save Sam . Castiel informs Dean he can't interfere due to how important Prophets are, but he impresses upon Dean how the archangel protecting a Prophet will intervene if said Prophet is in trouble to secretly let him know a way to save Sam . </P>

When do sam and dean first meet castiel