Baby Groot

When Baby Groot enters the battlefield, create two 2/2 green Grootling creature tokens.
When damage is dealt to either of those Grootling tokens, replace each one with two Grootling tokens.
When damage is dealt to any of the four Grootling tokens, replace each one with two Grootling tokens.
When damage is dealt to any of the now eight Grootling tokens, replace each one with two Grootling tokens.
When damage is dealt to any of the sixteen Grootling tokens, replace each one with two Grootling tokens.