My friend was playing Neeko and I was playing Sona. I had the DJ Sona skin equipped, and she tried changing into DJ Sona, but there was a big and noticable issue with that.
The character had no hair. And that makes it easy to guess for the enemy that it's a Neeko and not a Sona.
I mean, I'm glad that I have a skin that Neeko players can't just get for free, but at the same time playing DJ Sona while having Neeko in the team is a serious nerf for Neeko.
I though I should report it, because it seems like a bug. Maybe I'm wrong and Neeko purposefully can't copy Ultimate skins, haven't tried it with other skins.
Edit: Here's a screenshot: