Smiling, as QI will happily tell you, isn't as simple as just creasing your mouth into a certain U-shape we all know and love - as well as that, it's also about the eyes. Without the eyes communicating your happiness, it's not a real smile, apparently.
Tyra Banks - also known as the lady from America's Next Top Model - calls the act of smiling with both your mouth and your eyes "smizing", so bear that in mind when you're pretending to take an interest in your boss's butterfly collection at the next work barbecue.
We bring all this up because we thought you might be in the mood for something smile-enducing - and what better way to put a grin on your face than some snaps of a variety of animals mugging for the camera?
Well, exactly. So sit back, relax and enjoy owls, dogs, cats, hippos and more thinking of something rather amusing.