Are there any comic book heroes or villains who've never altered their costume

For DC think pre-New 52.

The only one I can come up with is Barry Allen’s Flash. But I could be wrong.
I guess there’s a bunch of young mutants on Utopia that haven’t been featured enough to warrant costume changes.

I’m thinking Captain America. Can’t remember Hal Jordan doing anything new with the Corps uniform either.

Captain America’s facemask changed after the first issue or so. There was also a time where he had armor.

Black Cat?

What changes has Spidey made?

Captain Ultra

He had the alien symbiote costume for a while. The design of the classic black and red changed around at some point as well, I think, then changed back.

DC’s Captain Marvel.

The Hulk may have changed skin color, but his costume has pretty much always been the same.

ETA: and has the Sub Mariner ever worn anything but that speedo?

Back at the begionning, Hulk wore a pretty neat purple “swimsuit”-type “costume”, rather than shredded purple pants. They experimented sat first with Banner neing able to choose when he became the Hulk (he stepped onto something that looked like a souped-up bathroom scale). At those times, he deliberately dressed for the part, rather than the way it was later on, with him willy-nilly wearing whatever purple pants Banner had on when he changed.

He had a ugly black suit with wings in the 70’s, more recently I’ve seen him in a similar black suit with a very deep V-Neck. My guess would be Doctor Doom, I can’t think of any changes he’s made off the top of my head.

ETA: I don’t think Ka-Zar has had any costumes aside from his loincloth and boots.

And there was the Mr. Fixit suit as well. Didn’t he have a purple singlet when he was the intelegent green hulk at some point.

Namor had a few other costumes besides the green scale speedos, like the black disco pants.

The truth behind the costume changes.

Is there a difference between stylistic changes in how the superhero is drawn and an actual change in the uniform/costume? That is to say, do the early versions of Batman with the exaggerated pointy ears mean that later Batman used a more realistic (?!?) cowl design?
Or is this an artifact of the change in artists?

Hm. Silver Surfer maybe?

I guess there’s always The Tick, though he’s not all that old of a character…

Mr. Mxyzptlk always wears an orange tunic with purple trim and a derby hat (in the comics at least – the cartoon version is all purple).

Bat-Mite might also fit.

When they first introduced him in the 1940s, Mr. Mxyztplk (they changed it to "Mxyzptlk later. I am such a geek) wore a purple business suit with a purple hat and was completely bald – not the “silver age” look with his orange onesie with a purple derby (apparently they resurrected the original version for one of the animated cartoons). And in Moore’s “Whjatever became of the Man of Steel” he looks completely different.

This explains SO much!
I have never had the pleasure of watching the instructive documentary, ‘The Incredibles’. I probably should remedy that soon.

Hal’s costume has changed some, mostly the amount of green that is below the belt line. enough that it looks like an altered super suit.

And I think there is some speculation that that is not a costume.