Chattering

Rodents chatter constantly, gnawing their little teeth together like their life depends on it. Okay, fine, so their life does depend on it. Right, right, I know that if they don't gnaw their teeth down, their teeth will grow up into their head and kill them. Constantly growing teeth must be a bitch, but that aside, it's still some really weird shit that none of us would ever do.
Well, that's a lie. I did it once to annoy someone at a party. It worked, and now I can't chatter my teeth anymore because I lost them in the fight. Never chatter around the guy who's been drinking Jim Beam all night.
(flickr photo John's Hamster, Crispy by wsilver; http://www.flickr.com/photos/psycho-pics/3079172298/)

Not Caring If They Smell

Tons of animals don't give a crap if they smell, and why should they: they're animals. They're supposed to not give a crap. Occasionally a dog will clean himself, and cats and rodents clean often, but I'm pretty sure that's less about smell and more about looking pretty (goddamn animal vanity), because they still smell afterwards.
Most humans do care if they smell, and if they don't, they're assholes. The people who don't give crap if they smell are the same people who don't give crap if they cut you off in traffic, accidentally trip you, or plunge the economy in the shitter while giving themselves a raise. It's just common courtesy to make sure you don't smell like a Limburger cheese factory everyday. But if an animal smells bad, they're being a typical animal.
(flickr photo Dirty and Happy by YouDooAllous; http://www.flickr.com/photos/youdooallous/2630128910/)