This anomaly is from the Pathfinder images and was discovered Keith Laney. A comprehensive analysis of the anomaly is here: 
Pathfinder Rover Rat??
Visit the site and decide for yourself as he shows the same rock from a different angle, and the "rat" is gone...

Is it a rat or a strange rock? You decide for yourself! But view Keith's Animation before you do...

Pathfinder... Or Ratfinder...?

Originally posted by bledforit, a member of ATS Post ID 3944334

Ah ! Lord Zorgon, we joust again sir! As always an interesting post whether someone believes or not, thank you for posting.

I think I may have found where the fuzzy little guy made off to when he left the rock, I'm trying to post a couple pics to show you.

We are looking for this little guy.

I think I found his friends in this pic, one standing up against the rock, his fur red from the soil and his tail sticking out as a sign of aggression. He is looking at the other critter marked by the arrow. This one looks a lot like the one by the rover, you can even see his tummy!.

Original Image: http://photojournal.jpl.nasa.gov/catalog/PIA10214

The one standing up is similar to this groundhog pictured on earth, 

Just a couple of observations, not saying they are real and I haven't been to Mars recently but, the one by the rover looks like its sitting on fresh earth like from a burrow. So does the one under the arrow. You can make out the paunch (stomach) of the one under the arrow.

Also the one standing against the rock, you can make out what may be ears and hind legs. 

As I said, interesting thread as always, I believe 100% percent in life beyond earth, I have not had the an experience of my own yet, (hoping) but a very close friend of mine interacted with a alien ship and its crew for 5 to 11 days when he was about 15 years old, I've known him for 20 years and never known a lie to come from his mouth. I believe him.

If mars had life and it was destroyed it might make sense that burrowing animals may have survived, isn't that what happened here when we lost the dinosaurs?

Ladies and gentlemen, the real mystery is not whether there is life on mars, the real mystery is how I finally figured out putting pics in my post! thanks for your patience.