How Titans pulled off those final season DC crossovers with Doom Patrol, Stargirl , and more

Titans has come to an end, but before finishing its epic run, the live-action superhero series managed to make connections with other TV shows.

The ninth episode of season 4, "Dude Where's My Gar," followed Beast Boy (Ryan Potter) on a solitary vision quest. It turns out that Beast Boy's ability to transform into any animal connects him to the Red, a force that bridges all animal life in the DC universe. Fans of Harley Quinn and Swamp Thing may be familiar with the Green, a similar force that runs through all plant life. But as Beast Boy goes deeper into the Red, he finds himself connected not just to animals, but to other DC universes.

The ensuing multiversal cameos — including Brec Bassinger from Stargirl and comic writer Grant Morrison — were the result of a collaboration between Potter and Titans executive producer Geoff Johns, who have a story credit on the episode in addition to screenwriter Bryan Edward Hill.

Courtesy of HBO Max Brec Bassinger as Stargirl on 'Titans.'

Potter grew up reading Johns' classic Teen Titans comics from the 2000s, and the two bonded during the run of Titans over shared nerdy interests like comics and pinball.

"At the end of season 3, I was not really feeling as though Gar had serviced any story thus far," Potter tells EW. "So I reached out and said, ahead of season 4, that I'd really love to craft some meaningful story for Gar, and they were open to the idea."

Potter and Johns worked from the basic idea that Gar needed to do some soul-searching and heal his internal child. The story referenced Morrison's classic Animal Man comics, in which he breaks the fourth wall and talks to his character, so the writer agreed to do a winking cameo. Bringing Gar closer to the Red also meant getting to use that cosmic life force as a counterweight to season 4 villain Brother Blood (Joseph Morgan) and his death-obsessed cult.

"I think it's an incredible opportunity that, in the heat of this season that is so focused on the taking of life and this rise of an antichrist figure via vampire lore, it was nice to just have a moment to breathe and experience the other end of the spectrum," Potter says. "It goes without saying that the opposite of death is life, and what better way of showing that than by going on a vision quest that heals the inner self? I really wanted the story to reflect a kind of experience people have been having at home after several years of hardship and mental health struggles."

Potter continues, "the climax of the episode was Geoff's idea to really feel this sense of interconnectedness and show how one world may affect another world, such that you can actually eavesdrop on the alternate world."

Courtesy of HBO Max Ryan Potter on 'Titans.'

The life-affirming story got even more fun by connecting back to Titans' beginning. Before it was on HBO Max, Titans originally premiered on the now-defunct DC Universe streaming service alongside Doom Patrol, Swamp Thing, and Stargirl. And so, Gar got a glimpse of Bassinger's Stargirl, Derek Mears' Swamp Thing, and ended the episode by landing in the middle of the Doom Patrol's mansion.

"We wanted to have all four of the live-action DC Universe shows from the service's launch represented," Johns told DC.com.

The crossover with the Doom Patrol, which was assisted by that series' showrunner Jeremy Carver, had a fascinating result: For the first time, Cyborg (Joivan Wade) finally showed up on Titans. Even though Wade's Cyborg has been part of the Doom Patrol show and Ray Fisher's Cyborg was part of the Justice League in Zack Snyder's big-screen movie, the character is most closely associated with the Teen Titans.

Courtesy of HBO Max Joivan Wade as Cyborg on 'Titans.'

"When Jovan got cast as Cyborg, I messaged him because I knew at some point that the relationship was gonna mean something," Potter says. "I grew up with these characters and that brotherhood between Beast Boy and Cyborg is incredible. It mirrored a lot of friendships I had growing up, that way of teasing each other in a goofy not malicious way."

Potter continues, "so Joivan and I built a friendship prior to ever working with each other, and we really checked in with each other over the years. We had the opportunity to hang out a lot in person. So once he was on set, it was just that homecoming feeling. It felt like we've been talking about this for so long, we fought for this for so long, and now it's happening."

At least it all finally came full circle before the end.

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