I need a lot of harmless, but hilarious pranks?

Alright, so I work at a preschool, and me and this other preschool teacher have a friendly rivalry going on, where we prank each other. It is during the day, at the preschool, and I need some SUPER FUNNY pranks. So far i have, i put her purse in the fridge and put ketchup on the back of the fridge handle so when she opened it she got ketchup all over her hands, and one time i got a glass of water and a cup of glitter and went up the stairs over an edge so when she walked under it, I dumped it on her, when she came back from her break. Stuff like that. Not night time sleepver pranks, no dirty pranks, and no hurtful pranks. :)