Supernatural is a series.
Castiel [ ˌkæstiˈɛl ] is a fictional character portrayed by Misha Collins on the CW Television Network 's American television series Supernatural . Supernatural is an American fantasy horror television series created by Eric Kripke . The fifth season concluded the series ' main storyline , and Kripke departed the series as showrunner . With its eleventh season , Supernatural became the longest-running American fantasy series .