MTGNexus

I'm brewing Urza, Prince of Kroog and I was wondering about it's interactions with Mirage Mirror. If you copy something that Mirage Mirror turned into, does the copy also revert back to being a Mirage Mirror at end of turn? Or does only the original have this trigger? (I know if you do not copy an artifact you need to Liquimetal Coating it first before you can use Urza's ability). Because that would allow me to make copies of opponent's stuff as well.

You will get a 1/1 Soldier version of whatever Mirage Mirror was copying. The mirror changes its copyable values to its target and sets a duration for this change. Urza(or any other copy effect) only sees the copiable values, not the duration of the copy, as it can't see "under" the copiable values to the original card.

Also, it's not a trigger, its a duration. Which is why it isn't copied. If instead mirage mirror gave itself a trigger along the lines of "At the end of turn this turns into Mirage Mirror." Then that would be copied.