The terrorists have really mucked up our holiday plans.
It's the last day of school and everyone is mucking up.
mishaps from the cast as they muck up the dances and songs.
Step cutting could really muck up the grading system!
I want him to be more affectionate sometimes, but I know he isn't because (not that he's frigid in the sense that he doesn't want to show affection) he just doesn't want to muck up.