What is a (harmless) silly childhood prank you remember doing?

One of my many student pranks was stuffing my horse, Lightning, into the Haiti mission school bathroom when I was 13 yrs old, to freak out our squeamish new Marilyn Munroe look-alike teacher.

I was hoping to hear her scream again, like she did after she saw a tarantula running across the floor during class.

I couldn't fit the entire horse in the tiny bathroom, so Lightning's head hung out into the hall. I stood in front of it and called the teacher, pretending to be sick. When the teacher rushed in, I stepped aside, revealing the horse, and her movie-worthy screams made it worth my trouble!

As an adult, I realized she was likely just playing along with our pranks, as I do with my own students, pretending to be scared of their cute rubber snakes, etc.