When it first began hosting videos in November 2005, YouTube was primarily a venue for posting and viewing homemade clips, but as its popularity exploded, users started posting all kinds of old and new television shows, music videos, political ads and DIY documentaries, dramas, comedies and other ephemera. These 10 videos all helped contribute to YouTube's success and changed the way we consume our media. Saturday Night Live's "Lazy Sunday" "Lazy Sunday," featuring Saturday Night Live's Andy Samberg and Chris Parnell, is YouTube's first greatest hit, and it's an example of the sort of content--short-form comedy--that is ideal for the YouTube format. "Lazy Sunday" was posted the day after it aired and quickly became one of the most-viewed videos on the site. NBC's lawyers freaked and asked YouTube to remove the video after 5 million viewings, but it has been reposted and removed numerous times since. Its popularity led NBC to make the video available through Apple's iTunes and has driven the availability of online "snippet" content culled from broadcast television. "Hillary 1984" Created and posted in March by Philip de Vellis, a democratic operative with connections to the Barack Obama campaign, the Hillary "mash-up" contains clips of Ms. Clinton's speeches inserted into a famous 1984 ad for Apple Computer. De Vellis lost his job at Blue State Digital, a design firm working on Democratic campaigns, after his identity was revealed on HuffingtonPost.com. Simple and direct, it remains the best example of YouTube's potential as a venue for political warfare, skillfully playing on Clinton's reputation as a purveyor of canned sentiment OK Go, "Here It Goes Again" Warning: Do not watch this video more than two times in one day. Excess viewing may result in humming the addictive chorus until epilepsy sets in. As music videos go, it is a perfect storm of YouTube popularity--an endlessly catchy tune, a simple yet original execution (how many times did they have to rehearse that eight-treadmilled routine until they got it right in one long take?) and a proud trumpeting of a low-budget ethos. Avril Lavigne, "Girlfriend" This spot on the list could just as easily have been given to music videos from artists like My Chemical Romance, Fallout Boy or the easily excited Fergie. The popularity of teenybop-pop, pop-punk and hip-pop on YouTube is an unfortunate side-effect of the site's democratic, populist ethos. And the frequency with which this category of poptastic videos makes it into the "Most Viewed" category is a testament to the apocalyptic horrors that await us should we ever give 13-year-old girls the right to vote. "Guitar" This is perhaps the best example of YouTube's strength as a talent showcase. With the understated simplicity of its title (simply, "Guitar"), the no-frills presentation of its subject and its jaw-dropping impressiveness, it is perhaps the purest example of a YouTube video. "Guitar" earns its perpetual place on YouTube's "Most Viewed" list by virtue of its unstoppable rock dominance. This kid shreds. And it is at the center of a whole sub-genre of YouTube videos: the webcam guitar solo. "Evolution Of Dance" Far and away the most-viewed video on YouTube, "Evolution of Dance" is one of the more interesting of a related YouTube sub-genre: regular people videotaped on stage. The site has blossomed as a forum for strange, impressive or hilarious acts--whether it's college students reenacting "Super Mario Brothers" or "inspirational comedian" Judson Laipply running through every popular dance craze of the past 50 years--to gain exposure beyond the original, usually small, audience. Pokemon Theme Music Video Call it "Doofus in a Room with a Webcam"--these videos are often interchangeable, distinguishable by the fact that they are usually desperate attempts for YouTube notoriety. They can be cute, like two girls in a bedroom singing along to the Pixies, or grating, like the Smosh guys singing along to the Pokemon theme song. In the competition for YouTube fame, they are like the kid in the plastic costume at the Halloween party--examples of the bare-minimum effort required to enter. Lonelygirl15: "First Blog / Dorkiness Prevails" A 16-year-old home-schooled American teenager named Bree narrates her story into a webcam, leading viewers on a voyage of life, love, the occult, abduction and self-obsession. Except she's really an actress, and the series is a hoax--scripted content passing itself off as a webcam confessional. When the ruse was exposed, it was an international news event, and millions of consumers heard the word "YouTube" for the first time. In the time since, Bree and friends have continued to post further webisodes that are, collectively, somehow more boring than the Law and Order: Criminal Intent episode they inspired. Stephen Colbert at the 2006 White House Correspondents' Association Dinner Stephen Colbert's feisty performance at the 2006 White House Correspondents' Association Dinner generated a lot of heat among the Beltway punditry, but it generated even more heat on YouTube, where it was heavily downloaded in the weeks following the event. At the demand of cable network C-SPAN, which initially broadcast the dinner, it has since been removed from YouTube's servers. Google Video now holds the exclusive right to show the video. Clips from Comedy Central's The Colbert Report and The Daily Show were among the most popular clips on YouTube during its formative months and helped build the site's popularity; now the two shows can generally only be seen on Comedy Central's Web site. Free Hugs Campaign The weepy guitar ballad. The long-haired guy with the velour jacket. The location inside a mall. There are so many reasons to hate this saccharine video, with music by the misnamed Sick Puppies--which makes the fact that it is strangely affecting that much more frustrating. Along with cutesy clips like "Hahaha" (an infectious laughing baby) and countless silly animal clips, it's consistently ranked among YouTube's most-viewed videos.