Bob, Dawn, and Rex are three dinosaurs that live with Dilbert and Dogbert. Since Bob and Dawn are clearly different species, it can be inferred that Rex is a hybrid. Rex and Dawn are rarely seen, whereas Bob is a semi-regular cast member. It can be assumed that Bob is just more outgoing. Bob also likes giving wedgies, especially to those that deserve it. Bob has worked at Dilbert's company once, in the Procurement division.