The Mimeoplasm

As The Mimeoplasm enters, you may exile two creature cards from graveyards. If you do, it enters as a copy of one of those cards with a number of additional +1/+1 counters on it equal to the power of the other card.

"He's an ugly little spud, isn't he?"
—Dr. Raymond Stantz

Secret Lair Drop

Outlaws of Thunder Junction Commander

As The Mimeoplasm enters the battlefield, you may exile two creature cards from graveyards. If you do, it enters the battlefield as a copy of one of those cards with a number of additional +1/+1 counters on it equal to the power of the other card.

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Specifically, if The Mimeoplasm as a copy of a creature card that enters the battlefield with a number of +1/+1 counters, The Mimeoplasm will enter with those +1/+1 counters and +1/+1 counters equal to the power of the other exiled card.

The two creature cards may come from the same graveyard or different graveyards.

Treat The Mimeoplasm as though it were the creature card it's copying entering the battlefield. Any "As [this card] enters," "[This card] enters with," and "When [this card] enters" abilities of that creature card will work.

You can't choose to exile just one creature card.

You choose which one The Mimeoplasm is copying and which one determines how many +1/+1 counters are placed on The Mimeoplasm as The Mimeoplasm enters.