5 Incredible Batman: The Animated Series Episodes You Never Got To See
4. How Did Batman Descover Batgirl's Secret Identity? Batman: The Lost Years
BTAS explored a lot of the Bat family. However, one side to Batgirl’s story that’s never revealed is how Batman knows her secret identity, and perhaps more importantly, how Batgirl discovered the true identities of Batman and Robin.
In an encounter in a sewer with some goons, Batman remarks that Batgirl needs to watch her right when she attacks to the left, as she has a significant opening that is exploitable by a competent fighter. A few days later, Barbara Gordon and Dick Grayson (who are dating, both unaware of the other’s secret identity) are playing a game of tennis, which Barbara surprisingly wins. Bruce then says he’ll give her a game himself, and despite being a prodigious talent, Barbara loses to Bruce. When she asks how he managed to beat her, he remarks that he’d observed a weakness in her tennis skills, and that she left an opening on her right. He then pauses and regards her for a second, before continuing the conversation, although it is in this moment he recognises her as Batgirl.
Later, after an argument with Robin, Bruce takes Barbara to the Batcave and reveals himself and Dick as Batman and Robin, and from here the comic transitions into the excellent episode ‘Old Wounds’ from The New Batman Adventures’.
It sound trivial, but it’s Bruce’s knowledge of who lies behind Batgirl’s mask that ultimately leads to Dick Grayson hanging up the mantle of Robin for good, so the details behind Batgirl’s full integration into the Bat family directly lead to the birth of Nightwing, and Tim Drake stepping into the role of the second Robin.