I come from A family of 14. So as you can imagine we didn't always get along. I waited A long time to exact some revenge. My older brother and I worked construction together. He always had to have coffee. Always the same white insulated mugs. More than one usually. I observed how he would tip his mug up when he drank. So I took the liberty to write on the bottom of his mugs in permanent black marker. In bold letters. "Owner F's pigs" He got A little upset, but it sure made good conversation. Took him A while to realize it.

Next time try drilling a little tiny hole right in the rim of the cup. Every time he takes a drink it will dribble on his shirt.

I only have one sibling....a brother 10 years older. I was the spoiled kid sister and I sure got him in trouble for things he never did. LOL!

I did the same to my brother.