Warning: The following contains SPOILERS for Gotham Knights episode 3, "Under Pressure."An infamous villain from the classic graphic novel Batman: The Dark Knight Returns has been brought into the world of Gotham Knights to serve as the archenemy of Carrie Kelley's Robin. The inclusion of Carrie Kelley as Robin in Gotham Knights' ensemble was one of the most surprising aspects of the show, given that Carrie has never been a part of the mainstream DC Comics' continuity and was originally created for an alternate future timeline. Gotham Knights seems to have followed this bold choice up by introducing a villain with deep ties to Carrie Kelley's origin story from the comics.

https://screenrant.com/gotham-knights-dark-knight-returns-villain-carrie-kelley-robin/