In "When We First Met," we spotlight the various characters, phrases, objects or events that eventually became notable parts of comic lore, like the first time someone said, "Avengers Assemble!" or the first appearance of Batman's giant penny or the first appearance of Alfred Pennyworth or the first time Spider-Man's face was shown half-Spidey/half-Peter. Stuff like that.

Reader Nicole K. wrote in to ask, "I was just checking out your latest "Look Back" feature with Supergirl and something stuck out at me. Supergirl knew Batman was Bruce Wayne. Was this still during the time when Batgirl didn't know? Was there a specific issue that Supergirl found out or discovered Batman's secret?"

Nicole is referencing this Look Back about the first issue of Supergirl's ongoing feature in Adventure Comics. 1969's Adventure Comics #381 had a lead feature by Cary Bates, Win Mortimer and Jack Abel. In the story, Supergirl is investigating a ring of robberies by a gang of young female criminals, all of whom seem to have no memory of their crimes after they get caught.

While doing some investigating of the case, Supergirl uses her X-Ray vision to look all the way to the Bat-Cave for some information...

She even goes there for more information...

And then later uses her X-ray vision to check it out some more...

Obviously, then, Supergirl must know Batman and Robin's secret identity, if she knows where the Bat-Cave is. She even mentions knowing Batman's other identity.

Later, it turns out that Batgirl was undercover on the same mission as Supergirl!

As a quick aside, as to Nicole's question of whether Batgirl didn't know Batman's secret identity at this point in time, technically she didn't, but I think the implication later is that she basically did figure it out and just didn't want to make a big hairy deal out of it.

Okay, this goes on to the question of - when did Supergirl find out Batman's secret identity?

The answer isn't clear, except that we DO have at least an instance of when we first learned that she DID, in fact, know their secret identities, and they, too, hers.

It came in Action Comics #270 (by Jerry Siegel and Jim Mooney) on what was Supergirl's busiest day!

All throughout the day, there have been all sorts of crazy emergencies. This was back during the time when Supergirl's existence was kept a secret from the rest of the world and she would only do superhero stuff during emergencies (like if Superman was off-planet). Well, thee were more than a normal amount of emergencies this particular day, including a cave-in at the Bat-Cave!

That, of course, proved that Supergirl knows their secret identity.

She is called to Superman's Fortress of Solitude later and she finds out that this is her 16th birthday and all of this was just Superman messing with her!

Superman notes that Batman and Robin were entrusted with her secret, which suggests, then that she was told theirs as some sort of reciprocal deal that Superman had going on.

So there ya go, Nicole!

If anyone else has a question/suggestion for a notable comic book first, drop me a line at brianc@cbr.com!