your help will be needed. My wife talks about an old Game Boy game she owned (1st game boy model), where you start as a boy around a Castle at a waterfall.
She thinks you directly start in a fight against a dragon or something, and must then jump into the waterfall to get into a valley.
Then she remembered finding one dodo egg, which eventually got born (not sure about that).
She's still haunted by the music.
i know its not much, but maybe someone will find it.
It's not Mario RPG, we already found that out.