SPRITE PROBLEM (RM2K3)

I did something wrong when changing sprites, but I'm not sure what... After importing a sprite sheet and assigning it's animations and such to a character, I tested the game. I think I missed a step somewhere, because instead of just the sprite, the sprite also has a solid green background, the color of the sprite sheet's background. I've tried checking the Transparen box, as I assumed it meant transparency, but that didn't work. Does anyone know how to fix this, or will I have to use new sprites?

Thanks, that fixed it.