Renegade Doppelganger

If Renegade Doppelganger becomes a copy of a legendary creature, you will have to put one of them into the graveyard as a state-based action.

If Renegade Doppelganger becomes a copy of another creature, it copies exactly what was printed on that card and nothing more (unless that card is copying something else or it's a token; see below). It doesn't copy whether the original creature is tapped or untapped, whether it has any counters on it or Auras attached to it, or whether it's been affected by any noncopy effects that changed its power, toughness, types, color, or so on.

If Renegade Doppelganger and another creature enter under your control at the same time, Renegade Doppelganger's ability will trigger. When the ability resolves, Renegade Doppelganger can become a copy of that creature.