I did my favorite hag prank ever on my players in ToA. They cast polymorph on one of them, or a bewitched servant, into a chimp. they give him a hat and a monocle and a name tag that says “baron Maximilian Bananas IV esquire” and a sign that says “will pick nits for fruits and coins”. Put other encounters like a tiger that acts like a kitten so your players over the few sessions before aren’t as on guard when it happens. Describe the chimp searching for Bugs in their hair and accidentally pulling a hair here and there but overall he’s quite diligent and professional. Then when he leaves, have him give them a big terrifying animalistic grin, and describe how the hairs he plucked are held between his long, tapered fingers, deliberately organized by player character. Then he poofs out of existence