WARNING: The following article contains spoilers for the Titans Season 1 episode "Donna Troy," streaming now on DC Universe.

While Titans has introduced a string of other superheroes in its first season, from Hawk and Dove to the Doom Patrol to the second Robin, there remained a question whether, beyond Batman, any heavy-hitters exist in this version of the DC Universe. This week's episode, Donna Troy," provides the answer.

Quickly establishing the years-long friendship between Dick Grayson (Brenton Thwaites) and Donna Troy (Conor Leslie), the episode opens with a flashback in which the latter pays a visit to Wayne Manor, surprising the young Robin as he returns from an upsetting confrontation with Batman's archenemy, The Joker.

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Sitting on Dick's bed, apparently doing homework, the teenage Donna informs the curious Boy Wonder that it's Diana -- that is, Wonder Woman -- to whom Bruce Wayne is talking downstairs. "It's a Justice League thing," she says, nonchalantly. "I talked her into bringing me along. I thought we could get into some trouble, but I guess I missed all the fun."

The exchange swiftly establishes three things: the older sister/younger brother dynamic between Donna and Dick; that this incarnation of Donna is (or at least was) indeed Wonder Girl; and, most importantly, that not only Wonder Woman but an entire Justice League exists in this live-action DCU.

Titans Donna Troy episode flashback

Until this, Titans' eighth episode, most of the "world-building" references had been to Batman, his rogues and Gotham City, which is completely understandable, given the central role played by Dick Grayson, and all that comes with him (his estrangement with his former mentor, his troubled backstory, his abandonment of the Robin identity, and so on). However, "Donna Troy" throws open the doors on the world in which the fledgling Titans exist.

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There's no indication in this episode which heroes, beyond Batman and Wonder Woman, may be part of this Justice League. But that such a premier team even exists suggests the possibility of such A-list crime-fighters as Superman, The Flash, Green Lantern and Aquaman (yes, Aquaman). Or maybe such a team existed, past tense. There's nothing to say those super-friends continued their alliance into Titans' present day, as several years have passed between that flashback and Dick and Donna's reunion in this episode.

That would certainly help to explain why, say, Beast Boy (Ryan Potter), who gushed about Batman and Robin, doesn't reference the Justice League when there's talk about forming a team. Maybe whatever united the elite heroes -- certainly not Starro in this DCU -- wasn't enough to keep them together.

Now streaming on DC Universe, Titans stars Brenton Thwaites as Robin, Anna Diop as Starfire, Teagan Croft as Raven and Ryan Potter as Beast Boy, and guest starring Conor Leslie as Donna Troy.