Cats live by a very strict policy of Fits & Sits. This policy dictated a large portion of a cat's decision-making process regarding closed spaces with an opening. When the space answers certain criteria, the Fits & Sits policy will not only allow the cat access - but encourage them to get inside and make themselves comfortable. The thought process in a cat's brain goes something like 'If I fits, I sits'. And indeed, if they fits, they sits.
Now, another interesting fact about cats besides their Fits & Sits policy, is that they're the absolute monarchs of the internet, reigning supreme through memes and endless cat content. The internet is like the big online cardboard box where they all do the Fits & Sits, making themselves comfortable in every corner of the internet.
Naturally, when you combine these two facts about cats, you receive a meowgnificent result: a lot of cat memes that fits and sits and adhere to the Fits & Sits policy completely. This is the most cat thing a cat can do - be a cat meme about the Fits & Sits policy.
source https://cheezburger.com/40231941/20-boxes-full-of-cat-memes-doing-the-if-i-fits-i-sits