Lolcats

Lolcats are photos of cats with humorous captions. They are a type of image macro, and are thus also referred to as cat macros. Lolcat images consist of a photo, sometimes photoshopped, with words typed over the photo.

Sometimes the captions are meant to be read as a comment from the cat (as if in a speech balloon), though it is also common for them to simply describe the depicted scene. They are usually intentionally grammatically incorrect, with errors in spelling and syntax.

I Can Has Cheezburger? is a weblog about lolcats.
Meme Cats is another one.
You can even make your own lolcats.