Douglas is a Crocopup who Thunk finds in a cave. At first Thunk is afraid of Douglas, thinking he's wild and hostile so he throws his shell at him. Eventually Douglas fetches the shell like a modern dog and Thunk makes him his pet.When Thunk first meets Douglas, he makes him roll over but he falls off the cliff, much to Thunk's dismay. Near the end of the movie Grug finds Douglas when escaping "the end" and saved him, Chunky the Macawnivore, a Trip Gerbil, and a grey Liyote, by putting them on the rib cage powered by Piranhakeets. He then becomes one of the family pets along with the other animals Grug had saved.
Douglas has the body of a deep-blue dog with a short tail, a white mane, stripes similar to a skunk's extending down to the tip of his tail, and a crocodile head. Douglas has a mouth full of sharp yellow teeth and an underbite, along with big yellow eyes with black pupils and irises much like other Crocopup.
Douglas's master is Thunk and is very loyal to him like a modern dog. But he is also loyal to Sandy since he gave her and Belt a ride at the end of the movie which tells he is very friendly to The Croods (family).