So, I'm playing Uni and got an opportunity to date someone. Well, some glitch happened, and the date got stuck before they could meet my sim, so I reset the sim via MC. When they were reset, all of their clothing and hair had changed from their default. I can't think for the life of me how to fix this. I figured it had something to do with Dresser, since the looks changed.

Dresser has an option called Check Outfits On Sim Reset, which wouldn't be an issue with Dresser but rather that Dresser found corrupt CAS items and revalidated their outfits. It's set to False by default, but it's also possible MC Reset may already invoke this (if you didn't change it yourself), as the note for this option doesn't specify if it's talking about resetsim or MC's more advanced reset.

The only 'fix' would be to reload a previous save and take preventative measures in the future- removing invalid parts and bad CC yourself.

Here's the thing, there was no CC on the sim that was reset, it was a sim made by EA for the Uni world, Bettie Franklin, to be exact. All defaults were changed just for that sim and no other. Yes, there is CC in the game (quite a bit actually), but as far as I know, my sim is the only one that makes use of them.