It's Aprils Fools' Day, which means pranks are in full swing. Whether you have tricks up your sleeves or not, you can get some great ideas from celebrity pranksters. From George Clooney's elaborate (and sometimes crazy) jokes on friends to Jimmy Kimmel and Matt Damon's ongoing battle to Ashton Kutcher's Punk'd past, there are plenty of famous jokesters. Though some of them, like Ellen DeGeneres, let others do their dirty work for them, others are more hands on — and in character — like Sacha Baron Cohen. Relive some of the best below, and be sure to watch out for any real-life pranks at your office today!