This is a fun activity to plan with a group of your residents in advance.
Get them together, pull out a white board and get brainstorming on they can prank the larger resident group at your community.
An example would be playing a funny trick in the dining room at dinner. The group could all eat their dessert first, stand up and start singing a song at a specific time or act out a dramatic scene.
It will leave your staff and other residents who aren't in on the prank confused, until the group shout's out, "April Fool's!"