The Ridiculous and Wonderful Rainbow Hat (Locker 37, Bk. 3)

When Riley Zimmerman needs help pulling off the greatest prank Hopewell Elementary's ever seen, the magical Locker 37 has the solution to her problem. It grants her a ridiculous and wonderful rainbow hat that clones anyone (or anything) that wears it. With the help of a bunch of Riley clones, an untrustworthy bully, and ten-thousand Ping-Pong balls, can Riley set up the most epic prank in Hopewell's history without losing her friends in the process?