Mirror Entity and Bighorner Rancher on the battlefield.
Bighorner Rancher does not have summoning sickness.
Steps
Activate Bighorner Rancher by tapping it, adding at least ({G} magic symbol) ({G} magic symbol) .
Cast Wirewood Symbiote by paying ({G} magic symbol) .
Activate Mirror Entity by paying ({1} magic symbol) , giving creatures you control all creature types and base power and toughness 1/1 until end of turn.
Activate Wirewood Symbiote by returning it from the battlefield to your hand, untapping Bighorner Rancher.