I solemnly swear I am up to no good
A fancy way of saying you’re about to cause chaos. It’s what Fred and George told Harry Potter to get access to the Marauder’s Map, because they’re the worst.
I solemnly swear I am up to no good. Now I can see where the principal is hiding. Time to run away.
I used the phrase and saw my friends plotting against me. I’m getting even.
I said the words and the map showed my teacher’s secret hiding spot. I’m going to prank her.