What do you think about me turning his alarm clock off so that he's late for work?
Why do you want him to be late?
I think it is a good prank to pull.
Making someone late for work is a bad thing to do. You could get them fired with your actions.
Wait what if he has to take shit from someone?
Then that is his business, and while you think you're being funny with this prank it could harm him a lot. Do you think it is worth the trouble for a small laugh to potentially lose someone close?