Bark the Special Nappy Time Friend is the stuffed crocodile toy that Hawk won in a claw machine, and gave to Croc as a gift, when the were kids. They decided to name him "Bark," because they thought it would be silly if crocodiles sounded like dogs.
The manufacturers of the Bark the Special Nappy Time Friend dolls accidentally created a very specific specific gateways linked to the deepest depths of Hell, with the chemical combinations found in the Bark dolls. The Barks were discontinued immediately, after about 1000 had been produced and shipped out. The manufacturers were able to recall and destroy most of these, but a few still remain scattered around the globe.
Bark was rescued, and at the end of Hawk & Croc Classic, Croc gave Bark back to Hawk, as a memento of their friendship. Bark currently lives on the night stand, next to Hawk's side of the bed he shares with Beth.