Obviously, a key feature for the survival of any species is the ability to differentiate between friend and foe. If you don't recognize a predator coming toward you, or don't realize the hot girl in the cave next door is one of your own kind, you're unlikely to pass your genes on to the next generation.
As a result we're hardwired to recognize other human faces. We may have left the caves way behind us, but the basic programming is still in place, and damn near impossible to override.
Anyone recognize this picture?
How long did it take you to see a face? Likely 1 second or less.
It's an area of Mars called Cydonia, photographed by the Viking 1 probe in 1976. Scientists at the time dismissed it as a coincidence of light and shadow, but that didn't stop a number of writers (particularly Erich Von Däniken) from including it in horseshit pseudoscience. It got great publicity in non-scientific circles as "proof" of life on Mars, or as evidence that extraterrestrials had previously visited our backwater solar system.
The area in question, of course, is still on Mars, and been imaged many times since then. Here's a shot from 2000: Doesn't look much like a face anymore, huh?
This is called pareidolia, and is, in my opinion, a fascinating phenomenon.
We see faces in clouds:
Pretty much anywhere:
Of course, with particularly famous faces, such as Jesus, Mary, or Elvis, this gets even weirder. Even before the internet age the news had occasional stories about figures (usually religious) being seen on toast, tortillas, trees, ceiling stains, and shadows on walls. With the advent of the web, however these sorts of things attract considerable attention quickly. Our continuing fascination with them is an ironic commentary on an ancient survival mechanism that keeps us from becoming something else's dinner.
It's also led to a rather bizarre cottage industry where you can now modify your toaster to put Jesus, or other famous faces, on your breakfast.
So my point here is that when you see a face on anything, whether it's bread, woodgrain, or a cloud, to just marvel at it. It's the way your fascinating brain functions to make sense out of random patterns, and keep you from becoming lion poop.
And beyond that, it's nothing.