Prototype Ooze

When you cast Prototype Ooze, exile a creature you control. Prototype Ooze's power and toughness are equal to the exiled creature's power and toughness.
{u}{r}{g}: Prototype Ooze becomes a copy of target creature an opponent controls until end of turn and gains this ability, except it's power and toughness are still equal to the exiled creature's power and toughness.