What is this?

If you know what this is, please -- enlighten me.  It's the second one like this that I have found in my yard.  It's obviously some type of seed... and apparently has a rather efficient method of transporting itself for multiplying in new locations... I just don't know what in the heck it is.

The skin "gives" pretty easily and it weighs nothing.  It's like a green bubble of air.

Sure I could plant it and see what happens, but my luck it would hatch instead of sprout, and who knows what I would have on my hands!  "Are you my mother?"

So if you know -- please tell me in the comments... Thank you!