Character Stars Question?

So I have heard a lot about how characters get stars, and are upgraded the more experience they get. But what impact does it have on the character? Is it just for experience?

I seem to remember from somewhere that stars were spent on the toy maker thing to unlock ToyBox toys.

I also read that the max level is 15, so does that mean that each character will only be able to unlock 15 toys in the toy box? (15 levels = 15 spins)?

My guess is levels are different from stars.

I remember hearing in one of the early videos that maxing out your character at level 15 unlocked some kind of new "skin" for the character. Does anyone know if that's still the case?

If that's true, Bullseye will probably a playable character and the "pink Bullseye" is his skin.