Ryan Reynolds appeared on Late Night With Jimmy Fallon, where he publicly confirmed that he will appear as both Deadpool and Green Lantern. While Fallon found the castings a "double whammy," Reynolds was more modest.
At his point [playing both roles] makes you just like an Internet hero, nothing really more than that.
Reynolds also mentioned he was "4-5 months away from beginning shooting" Green Lantern, but couldn't tell Fallon much more than that.
It's crazy, it's the only job I've ever had that I'm not allowed to really talk about. I think there's like a representative from Warner Brothers who I'm sure is following me around ready to blow-dart me if I say a single word,. I probably have a chip in me somewhere, like if I start talking about it, I'll just pass away.
Since Fallon had no idea what Green Lantern's powers were, Reynolds did offer him a basic understanding.
A lot of [the film] is sort of like a space epic and some of it is on planet Earth. [Green Lantern] has this ring and he's been chosen to have this power and the ring can kind of create anything that his will or his imagination can conjure up.
While Reynolds' explanation is pretty basic, he has been doing his homework. Late Night producer Mike Shoemaker Tweeted to Green Lantern comic book writer Geoff Johns that he made Reynolds deliver the Green Lantern oath.
I just went in Ryan Reynolds' dressing [room] and tested him on the GL oath. He nailed it!