Whenever a nontoken creature with power 4 or greater enters the battlefield under your control, populate. (Create a token that's a copy of a creature token you control.)
Any "as [this creature] enters the battlefield" or "[this creature] enters the battlefield with" abilities of the new token will work.
If you control no creature tokens when you populate, nothing will happen.
The new creature token copies the characteristics of the original token as stated by the effect that created the original token.
The new token doesn't copy whether the original token is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, color, and so on.