This creature is an amorphous mass of ooze coated with a slimy, protective membrane (think a biological equivalent of rubber cement). It's not very large (relatively, compared to many other fantastical monsters), it would fit inside a pot of spaghetti. It can be just about any color, but sludge brown is the most common. It has four stalks, each tipped with a bouncy orb, on top of its head and an oral cavity it forms when it wants to eat something.
This tongue is long, flexible, and muscular enough to bind and pull in struggling prey. The oral cavity has teeth along the edges, which could be spines or stiffened psuedopods or even sharp cilia.
This creature happens to be both flexible, tough, and resilient.
The question is, how feasible is this creature? What adaptations does it need to exist?