Whiplash Wordsmith // Vicious Verse

If an effect instructs you to choose a card name, you may choose the alternative prepare spell's name. Consider only the alternative characteristics to determine whether that is an appropriate name to choose.

If a prepared creature stops being a creature, it will still be prepared, and the copy of its prepare spell will remain in exile. That permanent's controller will still be able to cast it. The same is true if a prepared creature becomes a copy of something else, even if it's then a permanent without a prepare spell.

If an effect causes a creature to become unprepared, a prepared creature stops being prepared and the associated copy of its prepare spell in exile ceases to exist. If it wasn't prepared at that time, nothing happens.