There's no formula for creating a video that millions of people will be inspired to watch and tell their friends about, but if there were, it would have to include some portion of humor (often unintentional), embarrassment, obscenity, and plain old goofiness. Since the advent of YouTube in 2005, many viral videos have been made, but few surpass the popularity of these 25, um, classics.

Bush and Kerry Sing "This Land Is Your Land"

Remember this goody from the 2004 Presidential campaign? One of the first truly viral videos, JibJab's "This Land Is Your Land," created by brothers Gregg and Evan Spiridellis, recasts the Woody Guthrie classic with places and faces of the 2004 presidential campaign. The original was about pride and national unity, themes that sounded completely out of place in the context of the election, when the cultural gulf between Democrats and Republicans couldn't have been much wider. But for all that, the big heads of George W. Bush and John Kerry sitting on top of stick-figure, Shockwave-animated bodies was funny in and of itself, never mind the digs that the filmmakers throw at both candidates throughout the video. The 2004 election seems like a decade ago now, but JibJab's video brings it all back, and it's still good for some laughs.

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The Coke and Mentos Experiments

Who'd have thought that an eighth-grade science experiment would become the object of worldwide fascination? That was the effect of this viral video classic, and people are still checking it out on YouTube and a hundred other viral video sites. You simply drop seven or eight pieces of Mentos candy into a bottle of Diet Coke, stand back, and watch the geysers shoot out. Hundreds of people have now duplicated the experiment in their own versions of the original video, and the original's creator, Steve Spangler, has done numerous live performances of the beloved trick. Following is what we think is one of the first Diet Coke/Mentos videos to have appeared in shared video land.