Here’s one way to make your ad go viral: check out this choose-your-own-adventure video created by the agency Buzzman for Tipp-Ex (a sort of UK version of White Out in the U.S.), which already has more than 8 million views on YouTube. The ad, called “Hunter and bear’s 2012 birthday party,” starts innocuously enough with the two characters -- Hunter and bear -- sharing a birthday cake when a giant meteor falls out of they sky, threatening to end the world. After Tipp-Ex erases “2012” out of the YouTube title, the user is asked to enter any year they wish to replay the birthday party. You can literally enter any year you want, both before and after 2012. We won’t spoil the fun for you, but make sure you try various dates in history.