Which mammal is the most flexible?

Out of all four of Marvel's fantastic heroes, Ben Grimm undergoes the most difficult transformation, becoming the rock-encrusted, superstrong "Thing." While Ben's new visage makes him — to put it lightly — unique among humans, he'd fit in quite well among many animals. read more

Snakes possibly, some species can flex their whole bodies to engulf prey far larger than their own size. read more

The animal that is the most flexible is a very subjective question. Animals with skeletal structures that are flexible are cartilaginous fish and snakes. Otherwise perhaps a parasitic worm of some sort. read more