great funny pranks to play on a teacher?

in one of my classes me and my class always play pranks on this one teacher. she is usually late, so one or two people hide in various places during class, and try to stay hidden for the longest, without her finding us. so far the longedt time was 1 hour and 35 minutes, when alyssa hid in a cabinet. but she has found out most of our hiding spots by now and what is another good prank to play, that is easy, since the hiding prank is getting old.

hide her desk in the bathroom

I'm writing a play and my teacher told me to include something abstract. Help?