If you didn’t already know that hovering your mouse over any xkcd comic will show you some funny alternate text about the image, you are officially living under a rock.
The xkcd Alt Text extension for Google Chrome moves the alt text right below the image so you don’t have to hover your mouse to read it. Personally I think this ruins half of the fun of reading and finding the hidden text, but if you’d prefer it, here you are.
Also, xkcd is great.
XKCD Alt Text [Google Chrome Extensions]