OMG This is definitely one of the best issues ever!!!
There's more interesting stuff that just the revelation of the cover... yes a LOT more.
Ok for my surprice the Babs unmask was the first thing we see in the issue, then Wondergirl (WG for short) show us her "secret orange" an orange who tells her secrets (Yeah the orange isn't the secret) and work like those pyramids or billiard balls (for being more exactly, Bob Sponge's shell): You ask it some thing it tells you yes or no as answer.
Anyway, then Babs take them to her secret bat-lair (That is a part of her room) and it gets better... everyone wears retro clothes that Babs found and were of her father and unmask too!! We also see some Commissioner Gordon flashbacks (LMAO part). We see WG playing with oranges and making a "secret oranges Justice League" (and the oranges wear costumes :D See bellow), the cliche of using glasses to hide your identity, and WG in the classic red with stars costume.
And... finally we see WG''s funny and crazy dream ... which includes... tan tan taaaaan (now I'm giving you a cliffhanger >:D)
An unique issue you can't miss, one of the best in my opinion (and I read them ALL)
Oh wait... and my favorite part?... ALL the issue !!! but I still going to leave you an image (I'm not so evil)