Experiment: MovieClip following Curves

I’m sure this must be possible, and there’s gotta be an easy way to do it. I’m just not thinking of one right now.

I have a movieclip with a curved surface that is my ground. Then I have a movieclip that is my ‘hero’ and when the arrow keys are pressed, it will move right or left, and as it moves, i want it to follow the curves of the ground. I’ve seen it done, so I’m pretty sure it’s possible. I’ve looked around online for a bit, but didn’t find anything helpful. Does anyone have a suggestion how I might do this, or where I could find a reference as to how to do it?

Thanks in advance.