Shifty Doppelganger

Oracle Text

3U, Exile Shifty Doppelganger: You may put a creature card from your hand onto the battlefield. If you do, that creature gains haste until end of turn. At the beginning of the next end step, sacrifice that creature. If you do, return Shifty Doppelganger to the battlefield.

Card Rulings

10/4/2004 If the creature is not still on the battlefield at beginning of the End step, then you do not return this card to the battlefield.
8/1/2008 This card has received errata such that putting a creature card from your hand onto the battlefield is now optional. This means you no longer need a third-party to verify that you don’t have any creature cards in your hand if you don’t put something onto the battlefield.