I’m not sure Shadowhunters would get in on April Fools day but Simon and Clary would love it. Clary spent one morning crafting an exquisite stage makeup scar on her stomach to show to Simon at school and they both got detention. Simon had all sorts of trick items, like red hot gum and a fake hand. Luke and Jocelyn were more subtle about it, but they knew the event made Clary happy and every year she would find some small prank played on her. One year it was a Saturday so they stole all her left shoes.
The New York Wolf Pack probably goes big on April Fool’s day too. Luke spends the day on full defensive, talking down prank incited arguments and reminding his people to keep the peace. Then he sends Raphael half a dozen pictures of Dracula captioned “this is you”.
But the best April Fooler is Magnus. He has magic and he’s not afraid to use it, but his weapon of choice is the glitter bomb. Raphael, Ragnor, and Catarina spend April Fool’s day in mortal terror of getting attacked, although Magnus is at least kind enough to clean it up once the day is at an end. He also utilizes paint changes and hair colour switches to devastating effect.
The three of them would be the ones to introduce April Fool’s to the Lightwoods, in the most brutal way possible. Alec would wake up with all his socks replaced by neon ones, Jace would find himself with soap painted with nail polish. Izzy would get offered a salt covered cookie around noon time. Poor kids wouldn’t know what hit them.
Of course the year after that would be no holds barred, absolute chaos.