He's got my cat down perfect. Butter wouldn't melt in it's mouth. 
XKCD is my fave web comic. They have a little comment that pops up when you move your mouse over the comic (on their site, not in a hotlink) that is sometimes funnier than the comic.
Here are a couple of random ones:
mouseover: When I look into your eyes I see JPEG artifacts. I can tell by the pixels that we're wrong for each other.
mouseover: The rest is fear of raptors
xkcd.com/
Since you started the thread with a cat I thought I'd follow suite, but anything by Gary Larson is sublime.
