IYO: What fish start out CUTE & ADORABLE but are UGLY as sin the older they get?

[LeBon]

We have a starry Blenny awaiting its new home and the missus called it Steve. I thought cosit looked perhaps a bit of a nerd..Then just the other day it dawned on me, thats is not what she meant.

By the way, this guy is my hero right now

 

[Gtinnel]

A healthy Mimic tang looks very nice, that's a bad picture of it on LiveAquariua. Mine is a nice brown, with a yellow flashy tail like my Blue throat trigger.

I personally don't think the other pics I saw online look any better, I just used that one because it was the first one that showed both juvenile and adult in the same pic. I guess it's a good thing the IYO was added to the question LOL.
Maybe in person I would have a different opinion, I've only seen juveniles in person, and I like the way the juveniles look.