Graham denied enemies so they will probably not be there, although I could imagine some that would patrol some platforms, yes.
Shrinking platforms could be also nice, I think they shouldn't be difficult to implement as platforms are sprites and they use color collision detection. So we could use a platform animation with transparency... who knows. Maybe in Downfall 2?
The main character doesn't have any name. I thought about one, but he still remains unnamed. He is something between mouse, coala bear and maybe elephant a bit? There is also 2nd player character already drawn:
He has big eyes, huge legs, tentacles on his head and doesn't have any arms. Maybe he could be related to Nebulus, I dont know.
Both will appear in bigger form in the title screen, which is already created.