I NEED HELP!! -URGENT!?

Yesterday, my friend that i like, and i thnk he likes me back, but he has a girlfriend, played a huge prank on me. Im scared of clowns and he put a whole bunch of pictures of em in my locker! I screamed and threw my books at it and ran, i have asthma and i almost had an attack! He says i cant get him back but i need to prove i can. I just want to hear him say ahh you got me! I want somethng i can do at school. The other guy that helped i already got. I faked sneezed and threw water at him and he thought he got booger blasted at first. But the other one deserves somethng better, especially since im crushin on him. Somethng easy, fast, hilarious, but still safe. Im thnking i should pack some dog food in a bag and replace his lunch wth it. But i dont want to get caught breaking into his locker. Is it worth it? Or do u have better ideas? I need it by hopefully monday may 23 :) thank u!