Rule 707.4

Some effects cause a permanent that’s copying a permanent to copy a different object while remaining on the battlefield. The change doesn’t cause enters-the-battlefield or leaves-the-battlefield abilities to trigger. This also doesn’t change any noncopy effects presently affecting the permanent. Example: Unstable Shapeshifter reads, “Whenever another creature enters, this creature becomes a copy of that creature, except it has this ability.” It’s affected by Giant Growth, which reads “Target creature gets +3/+3 until end of turn.” If a creature enters the battlefield later this turn, Unstable Shapeshifter will become a copy of that creature, but it will still get +3/+3 from the Giant Growth.