Hi there! Just found this thread so I HAVE to throw this game out there. It's been bugging me forever!
Only saw it played once when I was over a friend's house. Pretty sure it was for the NES, but I could be wrong.
It was a side-scrolling platformer with a choice of characters, somewhat similar to Mario 2 (Doku-Doku Panic or whatever).
Each character had a different balance of speed, jump height, and health, from what I recall. They may have had other abilities, but I don't remember. For sure I can remember 3 characters. A little boy, a little girl, and a blob. The blob was super slow, couldn't jump, but had a ton of health.
I want to say I remember my friend called it "The Wacky Wizard of Oz" or something. But we were little and he could have been making that up, since a search for that yielded nothing helpful for me.