I solemnly swear that I am up to no good.

Give her hell from us, Peeves.

Mischief Managed!!!

I swear, the reason for full moons is so the gods can more clearly see the mischief they create.

…for nothing is ever so mischievous in its own place as it is out of it;

Now let it work. Mischief, thou art afoot. Take thou what course thou wilt.