Meme
A meme is an idea that starts on the Internet, quickly acquiring modifications from users around the world such that the root idea becomes the basis for multiple spin-off ideas, subsets of ideas, and other similar iterations. In this sense, a "meme" evolves, taking on a life of its own through the contributions of users of varied cultural backgrounds.
Most "memes" are humorous in nature. "All Your Base Are Belong to Us" was an early Internet "meme," and "lolcat" is a popular emergent meme.
Popular Internet Memes
LOL Cat
A "lolcat" is a meme (runaway, modified internet theme) in which the author takes a picture of a cat, and adds a funny, anthropomorphic caption that is potentially grounded in science fiction, or computer programming, subculture.
Either way, the goal of the "lolcat" is to be funny, self-referential, and build on previous iterations of the "lolcat" meme. Most "lolcat" images include references and liberal use of internet slang, such as "lol," etcetera.
"Lolcats" are receiving increased notice as a prominent part of internet subculture. The most prominent "lolcat" site is I Can Has Cheezburger?.
All Your Base Are Belong to Us
"All Your Base" was a meme popular in 2001, based on a poor Japanese to English translation of the 1989 videogame "Zero Wing." It spawned a massive video, based on the meme's title catchprase, a notable translation error.