DC Universe's Titans confirms Superman exists in the TV show's world during the second episode, "Hawk and Dove." Though only two episodes have been released, Titans hasn't shied away from the larger DC Comics universe. Batman's presence is felt in Titans, even if the Caped Crusader hasn't yet been seen. Plus, the show's supporting characters are ripped straight from the comics, including Konstantin Kovar and Amy Rohrbach. However, the story still focuses mainly on the core four Titans heroes: Dick Grayson aka. Robin (Brenton Thwaites), Rachel Roth aka. Raven (Teagan Croft), Kory Anders aka. Starfire (Anna Diop) and Gar Logan aka. Beast Boy (Ryan Potter).
In episode 2 of Titans, two new heroes join the fray - Hank Hall aka. Hawk (Alan Ritchson) and Dawn Granger aka. Dove (Minka Kelly). The episode is named for the older heroes and they play a pivotal role in the journeys of both Dick and Rachel - and it's revealed that Hawk and Dove were teammates to Robin when he still operated as Batman's sidekick in Gotham. But "Hawk and Dove" also makes reference to one of the other big three from the DC Comics, though Titans does so in a way that raises more questions than offers answers.
Titans' "Hawk and Dove" introduces the episode's eponymous heroes at the start, showcasing the pair in their superhero suits taking on a group of villains. When Hawk and Dove are next seen, Hank is recovering in the bathtub of their apartment, and Dawn comes into the bathroom to talk to him. DC fans won't be able to miss the fact that in this scene Dawn is wearing a Superman T-shirt - but no explanation is offered for why the character is wearing this shirt or what it means for the Titans' universe.
Of course, Dawn's Superman shirt raises the question of how exactly he exists in Titans' universe. It's possible the Big Blue Boy Scout is operating out of Metropolis as he typically does in the comics, and just hasn't come up in conversation yet throughout Titans' first two episodes. Unlike Batman, who's key to the show's story because of Dick's relationship to him, the existence of other currently operating superheroes hasn't been brought up yet. So, perhaps Superman is a fully realized superhero, and merchandise of him is available to people around the world. After all, fans did see something like this in Zack Snyder's DC movies, in which Henry Cavill's Superman became a worldwide phenomenon and the hero's merchandise was sold everywhere. (Titans doesn't exist in the same continuity as Snyder's movies, though, since that universe's Dick Grayson was killed prior to Batman V Superman.)
Still, it's strange for Titans to show one of its characters wearing a Superman shirt and not address the Man of Steel himself. It could be meant simply as an Easter egg, something that acknowledges the larger DC universe without having to deal with it outright. Certainly, Hawk and Dove and the rest of the burgeoning Titans team have plenty to deal with in their own lives that their lack of attention to Superman's presence makes a kind of sense.
However, a T-shirt is still a weird way to acknowledge Superman in Titans. Unlike Batman or other DC Comics characters in Titans - like those in Robin's phone - the T-shirt removes Superman from their reality a little bit. Superman T-shirts like the one Dawn wears exist in the real world where the hero is a fictional character. Since the TV show doesn't offer any explanation of the Superman shirt, it's unclear if the superhero actually exists in this world or is a fictional character to them as well. Though fans can debate what Dawn's T-shirt means for the existence of the Man of Steel in this DC Comics-based universe, we won't know for sure whether Superman truly exists in the world of Titans until the show confirms it.
Titans season 1 continues with "Starfire" Friday October 26 on DC Universe.