Batman: Legends of The Dark Knight #120, p. 22: First Appearance Cassandra Cain in Batgirl Costume

This one's got some great splash-page appeal to it featuring almost the whole Bat-family in that image (if only Deodato had squeezed Oracle in on a platform on the clocktower, watching them all leap!), with a few lead-up panels inset.

Mike Deodato, who'd gained a lot of attention in the nineties for his work on "Wonder Woman," was the penciller here, but his work in this issue (compared to WW) honestly looks a little rushed. Wish I knew why.

Still, here we have an essential moment: Cassandra Cain emerges, wearing the Batgirl costume for the first time. As the first DC hero in this tier with Asian heritage, she helped to diversify the line-up.

This early in her appearances, she still didn't even have a name; Oracle mentions as much explicitly earlier in the issue. By now, the characters knew her as David Cain's daughter, but Batman only calls her "our new friend" in a previous page.