A good joke for me has always been to tell a boss or coworker that Mr. Lion or Mr. Bear called while they were at lunch. Tell them they left a phone number for them to call back. Give them the number to the zoo. One year they said "I'm sorry Mr. Bear is in his cage having lunch right now, can I take a message?" Then they tried to get him to adopt an animal. He was so embarassed. It was great.
