Warning: This article contains spoilers from The Boys season 4, episode 6, "Dirty Business."

When Jeffrey Dean Morgan told Entertainment Weekly that he and Karl Urban are "the same f---ing motherf---er," he wasn't joking.

The latest twist from The Boys season 4 came in episode 6, "Dirty Business," during which it was revealed there's much more to Joe Kessler, played by the Supernatural and The Walking Dead: Dead City star. Yes, Kessler and Urban's Billy Butcher are old chums. He also happens to be a figment of Butcher's imagination.

Butcher didn't actually save Kessler's skin when they both served at the Panjshir Valley in Afghanistan. He left him there to die. Kessler now exists as a hallucination caused by the Temp V-enhanced tumor throbbing inside Butcher's brain. "I don't think he's like Venom," showrunner Eric Kripke tells EW, referring to the famous Spider-Man adversary of Marvel Comics. "I don't think he's a dude with his own point of view and wants to go eat chickens or whatever, but I think he represents all that's dark and malignant inside of Butcher."

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Shantel VanSanten returned earlier in the season as Becca, Butcher's deceased wife, representing his first tumor-induced phantom. She not-so coincidentally arrived around the same time Butcher started seeing Kessler.

It's a twist that brings to mind The Boys Presents: Diabolical, the eight-episode anthology spinoff featuring vignettes set in the world of the mothership show. Some are considered canon, some are not. One episode in particular, "John and Sun-Hee," involved a terminally ill elderly woman whose pancreatic cancer gets a life of its own after her husband exposes her to Compound V. That V-juiced cancer, however, was much more aggressive than Butcher's.

"Both Butcher and Homelander [played by Antony Starr], in very different ways, are wrestling with whether they're human or whether they're monsters," Kripke muses. "Kessler represents the monster side and Becca represents the human side of Butcher. Those two sides are at war with themselves, but they're all Butcher."

As the writers behind season 4 brainstormed a role for Morgan, a longtime fan of The Boys, Kripke says it was always the plan for the Kessler element to be a misdirect. "We wanted Butcher to really be dealing with his light and dark sides, and yet he was so isolated for so much of the story that we needed a way to dramatize it," Kripke continues. "The notion of literally the angel and devil on his shoulders came up pretty soon."

A flashback montage revisited all the past scenes audiences saw between Butcher and Kessler throughout the season thus far, showing how our tortured anti-hero was really speaking with nobody all along. That montage was not scripted, Kripke reveals.

"That was producing director Phil Sgriccia's brilliance," the showrunner says. "He laid out a rule to all the different directors: Whenever you shoot a scene with Jeffrey and Karl, you have to do a take where Jeffrey steps off and reads the lines off camera so that there's nobody there. He said, 'Because I know as an editor I would want that when that reveal comes.' It's a testament to how smart Phil is."

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There are now only two episodes left of The Boys season 4, which drops new installments every Thursday on Amazon's Prime Video. Butcher, with Kessler's voice screaming in his ear, now knows he could incite an airborne pandemic that could wipe out all supes on the globe should the virus from Godolkin University's the Woods lab be developed. We'll see what he decides to do with that information.

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The finale is set to stream on Thursday, July 18, on Prime Video.