From Freakonomics:
GameStation, a British computer game retailer, added an “immortal soul” clause to the contract signed by online shoppers on April 1, 2010. Thousands of customers agreed to the following stipulation: “By placing an order via this Web site on the first day of the fourth month of the year 2010 Anno Domini, you agree to grant Us a non transferable option to claim, for now and for ever more, your immortal soul. Should We wish to exercise this option, you agree to surrender your immortal soul, and any claim you may have on it, within 5 (five) working days of receiving written notification from gamesation.co.uk or one of its duly authorised minions.” Yes, it was an April Fool’s Day joke; GameStation will not be enforcing its ownership rights.
Lydia Loren has previously noted that the Alchemy Mindworks web page “provides that if a user fails to register software downloaded through their web pages ‘a leather-winged demon of the night will tear itself, shrieking blood and fury, from the endless caverns of the nether world, hurl itself into the darkness with a thirst for blood on its slavering fangs and search the very threads of time for the throbbing of your heartbeat. Just thought you’d want to know that.'” That one actually isn’t a joke, either, it’s an exercise of contract power against people who lack bargaining power, so they don’t bother to read the terms and conditions they are agreeing to.