You say this like I'm somehow in the know.
My first thought is poops, but catastrophic is a big ugly word for a poop that went south. (I guess all poops go south, technically.) Unless you blew a part of you that was inside into the outside. Then you could use as many big ugly words as you wanted to, because none of them would be enough to explain a fresh, slimy visual of your own colon.
Maybe this is in reference to a fat-bottomed lady who wore a specific outfit and then the consensus was that her ass did not look as good as she'd hoped in said outfit. This could be catastrophic in a personal sense, in the way that people are way to dramatic about how their parts look in stuff. I deem this inappropriate usage as I'm sure you still have your inner beauty.
That was a joke. There's no such thing as inner beauty. Big butts or feel bad.
This question also made me think of this:
But again (butt again) not catastrophic.
Short Answer: I hope, dear Asker, that you did not shit out the bottom of a miniskirt. That would be very embarrassing. Especially if it was plaid. I don't know why. The world is mysterious.