Yeah, that's kinda what happens when you put bright pastel-tinted characters in a pastel-tinted world.
As a solution to that, I'd suggest avoiding pure black outlines on anything that isn't a sprite, since toning down the bright pastel world would kill it.
OR you do nothing and let animation tell the viewer what is something which you can interact with, and what isn't.
I would suggest making the elephant-man a bit brighter though.
(I like it that you have the author's blessing for this project. It makes it all seem extra-cute, heh <3)