Unstable Shapeshifter

Oracle Text

Whenever another creature enters the battlefield, Unstable Shapeshifter becomes a copy of that creature and gains this ability.

Card Rulings

10/4/2004 The copy effect is not targeted.
10/4/2004 If a creature enters the battlefield that has some characteristic or ability set when it enters the battlefield, the copy does not get to make that choice (because it is not entering the battlefield). All values are zero and all checks for choices consider the choice not to have been made.
10/4/2004 If the creature has power/toughness that is continuously recalculated, so does this copy of it.
10/4/2004 When it changes “shape” to a new creature, any “enters the battlefield” abilities of the creature do not trigger.
8/1/2008 The ability is granted as part of the copy effect, which means it will be removed by any effects that would remove abilities regardless of when the effect was created.
8/1/2008 If an Unstable Shapeshifter is on the battlefield when another Unstable Shapeshifter enters the battlefield, the first one gets the second one’s triggered ability, so will copy the next creature that enters the battlefield twice. It will only do so the next time a creature enters the battlefield, because the second “becomes a copy” effect to resolve will erase the extra triggered ability.