I kind of like the idea that otters are secretly solving the world's mysteries and we haven't noticed yet. Look at that first one. He is clearly working something out in his mind palace.
The "Martin Freeman as a hedgehog" trend is equally amusing to me. Tumblr is horrifyingly addictive! I never knew so many animals could be so easily anthropomorphized.
I have a friend who used to raise and breed hedgehogs. They are surprisingly cuddly, for being such prickly things. And their bellies are delightful to pet. It's indescribable, haha.