How to design and add shadow sprite in the game?

I’m trying to add shadow sprite under the character sprite but as you know the shadow cannot be embedded into the character spritesheet at the same time because the shadow itself should be in different layer than the character sprite.

In fact it can be easily done if the character doesn’t translate inside the spritesheet. What I mean is that each individual sprite will have space allowing character to make a move for certain complex animation that doesn’t require external translation. Another reason is for character to have a proper offset position and will be properly aligned with other animations.

That’s it. My question is how we add shadow sprite in the situation like this. Any idea would be welcomed.

I always use CCLayer, so I can have as many CCSprite inside it. And I only use CCSprite if it’s only use single image.