Hey guys, I need some help with a "prank"

Okay so I'm a freshman (high school) in chess club. The club is run by students, and everyone is friendly and knows each other. So, we usually always play magic at the last 45 mins. This kind of aggravates one of the seniors. So the club is coming to an end, and we have a spirit day coming up, so he told us not seriously no magic costumes. Naturally, I'm going to wear a magic costume. So, do you guys have any ideas?