Continuing my evidence for how The Batman connects with Teen Titans, there are some characters that appear in Teen Titans that have implications for other existing characters in this universe.
First up is Speedy. Speedy's real name is not given in the Teen Titans series, but his appearance is clearly based on that of Roy Harper. While not explicitly stated in the show, comic fans know that Speedy is the side-kick of Green Arrow.
The Batman introduced us to Green Arrow and gave us his origin story. Speedy wasn't present, and may not have been active at this time. In the comics, The reason that Green Arrow and Speedy stopped working together was because, in Arrow's absence, Speedy became a heroin addict. After his recovery, Speedy made it his mission in life to battle drug lords and pushers. It's possible this is why Speedy is working with the Titans and Arrow isn't mentioned. In my timeline The Batman episode "Vertigo" takes place three years before the Teen Titans episode "Winner Take All", where Speedy first appears.
Next up we have Kid Flash. Kid Flash was voiced by Michael Rosenbaum, who was the voice of Wally West/Flash in the DCAU Justice League series. This lends more to the fact that this version of the character is none other than Wally West, the first and original Kid Flash. Kid Flash is one of the few characters in the series to fully resemble his comic counterpart. The Flash was alluded to in the episode "Lightspeed", when Kid Flash said "I work alone these days" referencing his partnership with the original Flash.
The Flash was first introduced in The Batman's fifth season. According to the DC Wiki, Barry Allen is under the mask. Alan Burnett said that he sees the character as the Barry Allen version, though scripts left it up to the viewer.
However, the biography of his action figure states that his identity is Wally West. Due to crew statements usually being more reliable than merchandise, the wiki considers him to be Barry Allen, as do I and most of the fandom.

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In this universe, Robin has worked with all of these characters, which gives him a cool connection to both Mentor and Side-kick.
Finally, we have kind of an oddball. Kyd Wykkyd, who clearly based his suit on The Batman's. Kyd Wykkyd was created exclusively for the Teen Titans TV series. The directors stated that they wanted a cool bad guy, so they made Kyd Wykkyd.
Other than aesthetics/costume design, the implication is he was inspired by The Dark Knight's look. Not much else to go on. Suit comparison:
