What's the most satisfying prank you've ever done to your sibling?

I (37M) was about, maybe, 10 years old that time. My sister is only a year older than me and she loves to belittle, bully, and make fun of me at every opportunity. To this day, I still love my sister as a family.
Anyway, my sister often volunteered to get mails from mailbox outside of the house. She does this because she want to be the first to tell my parents that our school sent letter probably about suspension from bus or school for something I tried to hide from my parents.
So, one day outside on Saturday morning, I rode my bicycle and I saw a garter snake on ground. It was small one-footer pencil thin snake. I picked up the snake into one of cargo pockets in my pant and rode back to home for lunch. As I was nearing to home, I took snake out and placed into our empty mailbox. I ran into house and I looked through window for mail to arrive. My sister saw me and she became suspicious. She shouted to mom that she's getting mail and ran toward to our mailbox. I watched through window with huge smile the snake jumped into her romper and it crawled out through one of her legs.
Fast forward today, my sister won't open mailbox anymore. Her husband continues to assure my sister that there's no snake in Alaska.


Source.