Karl is somewhat of a master prankster. Ethan Ross @JR95 always carries such a stern demeanor, and could really use a laugh to loosen up. Karl wanted to do a theme this year, so he kept the pranks all hockey related.
#1 - Tigerbalm in the jockstrap. This one is a classic and old as time. Ideally it's not super noticeable at the start, but once you start to sweat oh boy. He will be running for the showers as fast as he can. No one likes the burning sensation down there.
#2 - When he's in the locker room dealing with his burning issue, sneak in and put shaving cream in his gloves. He'll get the balm rinsed off, only to stick his hand into that.
#3 - Coat his visor with olive oil. As long as it's cold enough it shouldn't really be noticeable. Once he starts to breath on it though it'll loosen up and everything will look blurry. Bonus is he will probably need soap and a lot of scrubbing to get it off.
#4 - The classic frozen towel trick. When he is in the shower, Karl will replace his towel with a replica that he had stored in the ice box. When Ethan grabs the towel to dry off it will be hard as a rock!
#5 - That's probably enough for one day. Karl will take out Ross for a beer to laugh it off. Ross better not go to the bathroom though, otherwise he's getting stuck with the bill!