20 From 20/20: YouTube's Biggest Hits

Sept. 21, 2011 — -- Six years ago YouTube.com launched on the web and revolutionized video sharing. What began as a simple idea -- allowing anyone to upload and view videos, for free -- quickly transformed into a platform that connected the world.

Check out 20 of YouTube's biggest hits over the years.

1. Justin Bieber's Baby: The music video for "Baby" is the number one, most-seen video on YouTube with more than 625 million views. As if that wasn't impressive enough, the young star has two other music videos in the current top ten most-viewed category.

2. Charlie Bit My Finger: The most viewed non-music video comes courtesy of two adorable British boys and one swollen finger.

3. Evolution of Dance: Comedian Jud Laipply's took us on a dancing time warp, bringing out the inner Elvis and boy-bander in us all.

4. LonelyGirl15: In 2006 LonelyGirl15, otherwise known as Bree, intrigued Internet users with her personal video confessionals. Shortly after, the fascination with Bree turned to curiosity as followers wondered about her authenticity. The Los Angeles Times uncovered the truth and outed the lonely girl as a character made by three filmmakers.

5. Numa Numa: Just a guy and his webcam, lip-synching to an infectiously fun song.

6. Crush on Obama (Obama Girl): The 2008 Presidential election saw its fair share of satire, but nothing was quite like the video of "Obama Girl" Amber Lee Ettinger professing her crush for then, Sen. Barack Obama in nothing but her teeny bikini.

7. Randy Pausch's Last Lecture: Arguably one of the most inspirational videos on YouTube. In 2007, Professor Randy Pausch of Carnegie Mellon University was diagnosed with terminal cancer. With only months left to live he delivered this speech titled "Really Achieving Your Childhood Dreams." It is remembered as his last lecture.

8. Hahaha: This video proved laughter is contagious, even more so when it comes from this giggly boy.

9. Keyboard Cat: Cats are big stars on YouTube, but none are quite as famous as this musically inclined feline.

10. Where the Hell is Matt: It began in Bolivia and took us to places we'd never seen. The crazy dancing legs of Matt Harding brought viewers on an adventure around the world. The video, uploaded in 2006, was one of the first to ever go viral.

11. David After Dentist: "Is this real life?" That's the question that 7-year-old David DeVore had everyone asking. A trip to the dentist for oral surgery led to one of YouTube's most enlightening videos.

12. Dramatic Chipmunk: This 5-second clip of a sinister chipmunk has been viewed over 30 million times.

13. Kittens Inspired by Kittens: A bubbly tot tells us what kittens are actually thinking.

14. Chocolate Rain: Aspiring singer/songwriter Tay Zonday shared his -- let's call it unique – vocal style with over 70 million people since posting his video back in 2007.

15. Leave Britney Alone: It was the cry heard round the world. Chris Crocker's tearful plea to stop harassing Britney Spears after her much-panned 2007 MTV Video Music Awards Performance earned Crocker his 15-minutes of YouTube fame.

16. Annoying Orange: Just one, really annoying orange.

17. Will It Blend: This scientific series answers the simple question, "will it blend?" The videos, uploaded by Blendtec, show items like glow sticks and golf balls being put into a blender. Apple product lovers beware -- so far the show successfully blended iPods, iPhones and iPads.