Flavorfully and mechanically, this seems more green. Though I guess there is precedent in Pack Rat, I think Progenitor Mimic's green side might be better to look at here. You may also wish to limit this on a similar way to the mimic.

Yikes, yes, this goes exponential - 2 one turn, 4 the next, 8 the next, 16 the next. That's far too prolific for an uncommon.

Oh oops, I meant to give it "a copy without this ability".

Right. That's a lot better.

However, it might still be too good. Compare Thraben Doomsayer, Puppet Conjurer, Breeding Pit, Genesis Chamber, Awakening Zone, Nuisance Engine, Wall of Kelp. This is cheaper than all of them.