Jensen Ackles on 'The Boys'' 'Supernatural' reunion episode: 'It was fun to watch them struggle'

Misha Collins (Malchemical), Antony Starr (Homelander), Jensen Ackles (Soldier Boy) and Jared Padalecki (Mister Marathon) in 'The Boys.' (Jasper Savage/Prime Video)

Eric Kripke, the showrunner of Prime Video's The Boys, also created Supernatural, which ran for 15 seasons on The WB and then The CW. Kripke then cast that show's star, Jensen Ackles, in The Boys as Soldier Boy, but the series' latest episode is a full-on Supernatural reunion.

In the episode, Antony Starr's Homelander and Ackles' Soldier Boy go to LA to talk to a supe named Mister Marathon, who they're told knows something about V1, a substance that can make Homelander immortal. Mister Marathon is played by Jared Padalecki, who costarred with Ackles as Sam Winchester in Supernatural.

"They brought him in as a bit of a cameo appearance," Ackles told ABC Audio. "Kripke's always got crazy ideas up his sleeve. This certainly was one of them,and we had a lot of fun."

Also in that episode, Homelander and Soldier Boy encounter another supe, Malchemical, played by Misha Collins, who was Castiel in Supernatural.

"It was good to mix it up with him again, and with Misha as well, and see how they handled the deep end of the Kripke pool that is The Boys," Ackles added. "I think they did OK, but it was fun to watch them struggle."

What did the two struggle with? Well, let's just say there's a lot of blood and gore, several deaths and general mayhem.

By the way, there are a number of big-name stars who make cameos in that particular scene, in addition to the Supernatural guys. We won't spoil it, except to say that, in a meta moment, one of them is Seth Rogen, who happens to be one of The Boys' executive producers.