Rulings

• All of the tokens enter the battlefield at the same time.2019-01-25
• Each token copies exactly what is printed on the creature and nothing else (unless that creature is copying something else; see below). It doesn’t copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and/or Equipment attached to it, or any non-copy effects that changed its power, toughness, types, color, and so on.2019-01-25
• If the copied creature is copying something else, each token enters the battlefield as whatever that creature is copying.2019-01-25
• If the copied creature has {X} in its mana cost, X is 0.2019-01-25
• If the entering creature leaves the battlefield before Mirror March’s ability resolves, use that creature’s last known existence on the battlefield to determine the token’s characteristics.2019-01-25
• Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any “As [this creature] enters the battlefield” or “[This creature] enters the battlefield with” abilities of the copied creature will also work.2019-01-25