Enchant creature you control
Enchanted creature doesn’t untap during your untap step if Cocoon has a pupa counter on it.
When Cocoon enters the battlefield, tap enchanted creature and put three pupa counters on Cocoon.
At the beginning of your upkeep, remove a pupa counter from Cocoon. If you can’t, sacrifice it and enchanted creature gets +1/+1 and gains flying. (This effect lasts indefinitely.)