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.
2011-09-22
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.
2011-09-22
The two creature cards may come from the same graveyard or different graveyards.
2011-09-22
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.
2011-09-22
You can't choose to exile just one creature card.
2011-09-22
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.