In our Supernatural: Road to the End retrospective series, we’ve been revisiting some of the key characters and recurring guest stars who helped make the show into the fan-favorite phenomenon it became over its 15 seasons on the air. We’ve talked to Mama Winchester (Samantha Smith); Charlie Bradbury (Felicia Day); Bobby Singer (Jim Beaver). and Rowena (Ruth Connell), and we’re ending our journey with the Winchester brothers and their closest ally, Castiel. Here, Jensen Ackles,…