Question: At What Point is it not derivative?

I started trying pixel art recently (I'm not an artist) and found using existing spritesheets as templates quite helpful to get the style, proportions, and poses I'm looking for. I am however worried about plagiarizing other people's work using this method.

I put together a quick transformation as an example:

Using the Earthbound character on the left as a template, at what point, if at all, does my character cease to be a derivative of the original?

1. Change color pallet, clothing, and minor linework. Different hat / hair.

2. Change face and minor body structure in hands / feet.

3. Remove shadow and adjust linework. I would add my own shadow outline here.

4. Squash character to more drastically alter the body structure and re-work linework.

I'd say that by the third one it's no longer derivative. Maybe some others would say the second one, but as the general outline is the same I would stick to changes in body structure/third character. (first is the original)