It's due to one of your favorite things: Flavor Pairings!

Before we go further, let's take a step back and consider what flavors are and how they interact. If you were to hold a microscope to most Western dishes, you would find an interesting but not all-too-surprising trend. Popular food pairings in this part of the world combine ingredients that share like flavors, which food chemists have broken down into their molecular parts — precise chemical compounds that, when combined, give off a distinct taste.

Most of the compounds have scientific names, though one of the simpler compounds is acetal, which, as the food chemist George Burdock has written, is "refreshing, pleasant, and [has a] fruity-green odor," and can be found in whiskey, apple juice, orange juice and raw beets. On average, there are just over 50 flavor compounds in each food ingredient.

A nifty chart shared by Scientific American in 2013 shows which foods share the most flavor compounds with others and which food pairings have the most flavor compounds in common. Peanut butter and roasted peanuts have one of the most significant overlaps (no surprise there). But there are connections that are more difficult to predict: strawberries, for instance, have more in common with white wine than they do with apples, oranges or honey.

See, the rat understands! Pairings!!

The same recipe works for Internet pics!  Pairings!  Cat's and boxes, cats and watermelons; cats and water, cats and dogs...the combinations are infinite!

So... Cats and anything?

Just wait until they get to dogs! Dogs and snow; dogs and dogs; dogs and polar bears; dogs and cats; dogs and bones....the combinations are doubly infinite! :-)

You pretty much have the essence of http://reddit.com/r/aww

We can write a program to generate all the combos, but then we'd need to figure out which ones are aww.

All the ones you mention sound like Aww to me.