You couldn't even say it's the worst outfit ever, because I think that award has to go to Miss Katherine Juno Pryde of Deerfield, Illinois for her infamous entry "Colorblind Disco Zap Girl."
Panel from Uncanny X-Men #149 (September 1981), script by Chris Claremont, loose breakdowns by Dave Cockrum, finishes by Joe Rubinstein, colors by Don Warfield, letters by Janice Chiang
Yep, this crime against optic nature debuted in Uncanny X-Men #149 and lasted through the following issue, where Magneto took such pity on her fashion sense that he spared the X-Men from their untimely deaths by magnets. You can try to claim it's not canon because it wasn't lettered by Tom Orzechowski (which, come to think of it, is a really good way to determine your personal X-Canon), but it happened. As Cyclops is fond of saying: "AIEEEEEEE MY EYES!"
This krazy kreation by Kitty is also an occasion for another "Professor X Is a Jerk" entry:
Chuck is really critical of Kitty's "costume" (note that word), even though, hey, Charley: pot, meet kettle:
Panels from Uncanny X-Men #193 (May 1985), script by Chris Claremont, breakdowns by John Romita, Jr., finishes by Dan Green, colors by Glynis Oliver, letters by Tom Orzechowski
So I wouldn't be that critical, Professor. Well, at least it coulda been worse...it could have been Thor's outfit from Thor #498:
Panel portion from Thor #498 (May 1996), scriot by William Messner-Loebs, pencils by Pino Rinaldi, inks by Andy Lanning, colors by Marie Javins, letters by Jonathan Babcock
Anyway, my point (you know the rest of that phrase) is that this infamous Kitty Pryde/Sprite/Ariel/Shadowcat/Li'l Intangible outfit is seen again, years later, in Wolverine: First Class #12, a continuity implant tale that takes place immediatel following X-Men #150. Say goodbye to Kitty Pryde, the Disco Era.
Panels from Wolverine: First Class #12 (April 2009), script by Fred Van Lente, pencils and inks by Scott Koblish, colors by Ulises Arreola, letters by Joe Caramagna
Pull up your seats, students: Professor Logan is about to tell us the official term to refer to one of those skintight unstable-molecule outfits all our favorite superheroes (except Lockjaw) wear.
Naturally, not everybody agrees on this terminology.
By the end of the comic, and keeping with the universal truth that Cyclops is a putz, Kitty makes her choice of not only what she wants to call that yellow and black outfit, but also who she wants to be her tutor in learning how to protect a world that is sworn to hate and destroy them.
So, as we have now learned, Wolverine calls the blue/yellow and/or brown/black outfit he wears a uniform. He never, never, ever calls it a "costume."
Panels from Wolverine: First Class #15 (July 2009; three months later), script by Peter David, pencils and inks by Scott Koblish, colors by Ulises Arreola, letters by Joe Caramagna
Oh for crying out loud.