This is something fans have been waiting for since the character left the show after the Season 2 finale, “All Hell Breaks Loose: Part 2." John was the father of the show's two main protagonist, Sam (Jared Padalecki) and Dean (Jensen Ackles) Winchester.
According to Entertainment Weekly, the episode is currently shooting in Vancouver, Canada, the go-to spot for many film productions because 1) it's cheaper and 2) the location can pretty much be transformed into literally any other point on the globe.
“We’re incredibly excited to have Jeffrey back for this milestone episode, and think fans will love what we have planned for his character… and a few other surprise guest stars," said co-showrunner Andrew Dabb in a statement.
Morgan's career has ballooned in the years since he left Supernatural. For example, a year after his last episode, the actor appeared in Zack Snyder's adaptation of Wachmen. Of course, we now know Morgan as the Saviors' bat-wielding (former) leader, Negan, on The Walking Dead.
The 300th episode of Supernatural will most likely air on The CW Thursday, February 7, 2019. Episode 296, "The Spear," airs tomorrow before the series breaks until January 17 of the new year.