User blog comment:Rassilon of Old/Ep. 124 "Performance" discussion/@comment-4998131-20120407235546/@comment-1038387-20120408104009

It doesn't look much like it. Just the standard circus outfit, they've been wearing that for years. I've read Nightwing YO a long time ago, and it's around here... somewhere... (not going to dig through boxes) so I can't recall if that's entirely accurate (though i'll give it to you). The Nightwing costume currently used, the black unitard with the blue (and now red) bird, was actually not the original costume

Nightwing and Flamebird were actually Kryptonian superheroes, Van-Zee and Ak-Var. Nightwing (retroactively) based his identity on them not after a trip to Kandor, but after Superman told him about them. Post-Crisis, they were Lor-Zod and Thara Ak-Var, during World Without Superman, World of New Krypton and War of the Supermen.