Interesing - and baffling! - question from a Chaos Sealed side event, at GP LA.

Abbi casts Polymorphous Rush, paying the Strive cost to target three of her creatures - let's say it's a Grizzly Bear, and two Ornithopters (because they're not that relevant).

When it resolves, she chooses Nick's best creature to copy - let's say it's a Carnage Tyrant (for those following along at home, here's the first cool thing about P-Rush - the creature to be copied isn't targeted)(I *did* mention, this was Chaos!).

After all that, Abbi casts Fated Infatuation, and targets her (not-quite)Grizzly Bear, which is now a copy of Nick's Carnage Tyrant. (With me so far? hang on, now it gets interesting…)

On Nick's turn, what is that token creature? A copy of Carnage Tyrant, still? or is it a copy of that Grizzly Bear?

I guess the question really is this: the 2nd copy effect is copying a copy effect with a duration (until end of turn); duration isn't listed as a copiable value, but copying a copy effect does copy that copy effect, which suggests it's also subject to the duration.

Great Minds didn't think alike, so curious minds want to know!

d:^D

P.S. - I did thank Abbi for the best rules question of the day!

Abbi's Fated Infatuation token is and will always be a Carnage Tyrant…barring intervention from the players, of course. (Abbi could, after all, cast another Rush and turn it into something else temporarily, or Nick could cast Mirrorweave, or they could do any of a million other things to change it.)

When you copy something that's been turned into a copy of something else, you're not separately copying both the original card and the effect that's turning it into a copy of something else. What you're copying is only the copiable values of that card. Those values happen to have already been modified by the other copy effect, so the values you receive are the modified ones.

Once Polymorphous Rush's effect wears off during the cleanup step, there's no longer anything saying that the Grizzly Bears is a Tyrant, so it's not one any more, but the Fated Infatuation token is still a Tyrant, because those are the values it copied–the fact that it'd look different if you copied the same permanent with something else now doesn't matter.

This is explicitly laid out in the rules for copying objects:

706.2b Once an object has been copied, changing the copiable values of the original object won’t cause the copy to change