20 easy pranks that are actually really good

To be clear, many pranks are mean, and even more of them are a waste of perfectly good office supplies. But there are a few pranks that are still pretty good, even for people who aren't members of the "epic prank" community.
Is April Fools' Day coming up? A co-worker's birthday, perhaps? Are you simply jonesing to do some pranks this week? (Why?) Then consider doing one of these pranks — they're low-effort, high-reward, and do not involve spilled liquids of any kind. 
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