Barbara Gordon, aka Oracle (Might be some spoilers)

[Linus Hyper]

Okay, so this caught up with me just now.
In Arkham Asylum, Oracle sounds like an adult woman in her middle 30's or even early 40's, while in Arkham Knight she appears as a teenager.
It makes sense that's she's very young in Arkham Origins, since that game takes place very early in Batman's life. IIRC she is not in Arkham City?

[ShikenNuggets]

She's not really a teenager in Arkham Knight. She definitely looks younger, but she could easily be in her late 20's or early 30's (which works if she was a teenager in Origins).

And she was in Arkham City. Or, at least her voice was.

[Linus Hyper]

I suppose that's plausible. So she was in City after all. Been a while since I last played it.

[Ophidian]

Barbara Gordon is in all of the games, but only appears physically in Arkham Origins as a teenager, and in Arkham Knight in two different timeframes (as Batgirl, shortly before being shot and paralyzed by The Joker. And as Oracle, years later after surviving Joker's attack and ending up in a wheelchair).

Oracle is also voiced by different actresses throughout the franchise, which explains why she sounds different in each of the games.