An meme is a cultural item that is transmitted by repetition in a manner analogous to the biological transmission of genes. (1)

The phrase was originally coined by Richard Dawkins in his book The Selfish Gene(2) to describe the tendency of cultural or technological ideas to be spread from area to area. Now, the word meme is most commonly used to refer to various forms of media spread across the internet in a self replicating fashion. Viral videos, while not necessarily meme in and of themselves, often become memes as the original video is altered or expanded upon. While some memes, such a lolcats, are based on the concept of taking an image and photoshopping it, other memes evolve by subverting the original intent of the media by using it in a different context than was originally intended. A prime example of this is "Rickrolling" which involves linking to Rick Astley's video for Never Gonna Give You Up while labeling the link as something else.

The primary source for internet memes comes from the message board 4chan. 4chan originally started in 2003 as an image dumping site for a subsection of the forums, and its popularity quickly spread, leaving it to become the largest English language image board in the world. (3) Due to the prevalence of memes on the board, along with the widespread impact 4chan has had on internet culture, the founder of 4chan, moot, was voted Time Magazine's most influential person of 2009. (4)

While some memes gain immense popularity very quickly, others never gain popularity or have a slow growth over time. While it is unknown exactly what causes a meme to become successful, there are many factors which come into play. The first factor is exploitability. If a piece of media is exploitable if it is easy to alter and replicate, such as a video filmed in front of a green screen. The second factor is that the media must be compelling or interesting to the culture spawning it. Finally, the media must encourage replication. It is not enough for something to be exploitable, but it must also, intentionally or unintentionally, encourage participation by those who view it. Encouraging participation and being exploitable are not necessarily the same thing, as Christian Bale's rant was not particularly exploitable, but was instantly mockable.

Memes come in many forms, the most common of which involves photoshopping images. Lolcats are, by far, the the most prolific of this type of meme. Usually the use of this particular genre of meme involves adding text to an already existing image, as is the case in lolcats and demotivational posters. These images are easily exploitable and encourage participation in the audience. Photoshopping images is not limited simply to adding text however. Many memes involve taking an existing picture and putting it into a different context by adding it to another image. This practice includes such memes as disaster girl, some variations of the "Imma let you finish" meme and various others.

Other memes are based on video. The Star Wars Kid is a prime example of how a video becomes a meme by being highly exploitable, interesting to a wide audience and unintentionally encouraging participation through its exploitability. Also included within this category is the prime example of subversion and appropriation in a meme, rickrolling.

Rick Astley's Never Gonna Give You Up was originally a number one hit single in 1987, but gained popularity on the internet in 2008 as a prank. It became so popular that for April Fool's Day 2008 changed all the links to videos on its homepage to the rickroll video. Rickrolling also represents a meme that gained prevalence in popular culture as well. It made an appearance during four women's college basketball games in 2008 as a Rick Astley impersonator lip-synched the song before games. Then, during the Macy's Thanksgiving Day Parade in 2008, the float for the TV show Foster's Home for Imaginary Friends rickrolled the nation by having Rick Astley appear out of the float and lip-synch his song on live TV. Even Speaker of the House Nancy Pelosi got in on it when she linked a Rickroll on her youtube hub.
Dawkins, Richard. The Selfish Gene. Oxford University Press. Oxford, New York. 1976,8599,1894028,00.html