This is awesome! I like how cute the lil mushroom guys are. I would definitely recommend putting in a HUD that tells the player how to use the ability though, because I literally clicked every button on my keyboard to figure it out. Tried clicking the mouse too.
I'd be interested to see a full game where this mechanic was useful! I imagine it would replace the heart/hp system, and when you're down to your last baby, it grows up to be a big mushroom and then you start over maybe?