the "Midvale School for the Gifted" one, probably.

--Stuart

http://www.flickr.com/photos/tmlsb/228428783/
 

Ooh, good call...
 

Howdy howdy howdy!
 

My sister once gave me a birthday card of the one you've got posted here.

As far as my favorite goes -- didn't track down an online image of it to link to, so will just have to describe it:

It's the one where several cows are standing around in a pasture, and one of them is spitting some stuff out of its mouth and it looks really mad, and the caption says, "Hey, wait a minute, this is grass! We've been eating grass!"

Two close runners-up for me are:

Two space aliens in a flying saucer, flying low and fast over a crowded city street, people running away wildly in fear, the space aliens grinning broadly, and the caption (the space aliens talking), "Eeeeeee - haaaaaa!"

And, a chef in a restaurant kitchen holding a lobster, just about to drop the lobster into a pot of boiling water, and the lobster is saying, "There's no place like home! There's no place like home! There's no place like home..."
 

The "no place like home" is one of my faves, but CAT FUD is the king of cats in the Far Side, I agree with you there.
 

Here's one of mine. http://www.centresupply.com/_borders/pilots.jpg. The inevitable conclusion, though, is that I've left many I love out...
 

http://earthhouseholder.blogspot.com/2005/12/jerks.html

Here's one of my favorites.
 

The one with the silhouettes of a wolf holding out flowers to a sheep, with the caption "From the beginning, their affair was doomed: Harry cared too much what the pack would think, and Agnes just ate the flowers."
Also my favorite-ever valentine card, so if anyone finds it, give me the link!