The only member of the genus Setonix, Quokka, is a plant-eating mammal of Australasian family, about the size of a domestic cat. It is considered as the happiest critter, as seen in many photos around the web. Human presence has been adapted in the environment by fearless, appealing and inquisitive quokkas, in admirable fashion.Why are they smiling? Consider a dopey grin face of great white shark. Clive Wynne says about quokka’s Mona Lisa smile; “It is an accident of evolution”.The natives and tourists of Australia find it the most interesting activity, to get a selfie with this happy-go-lucky creature. Let’s have a look!