Clan Doogen are an extended family who all share this same body plan - canine head, extra pair of legs. They're known throughout their world (whichever that is; I haven't decided yet) as experts with all sorts of vehicles - there are Doogen sailors, couriers, pilots, and chauffeurs. It's the family business.

There is the matter of the clan curse, though. Long ago, the clan's founder - Captain Valentine Doogen - was infamous for his philandering ways. His unfaithfulness drove his wife to seek out the help of a witch who cursed the captain with the Doogen shape (just what they were before is irrelevant), as well as anyone he'd ever slept with. Suddenly it was blindingly obvious just who'd been with him (although they'd all been suddenly changed without warning, which caused its own share of problems). The problem is that the curse didn't stop. Anyone born to a Doogen becomes another Doogen, and the curse extends from there. This is why everyone in the extended family shares the shape - once you're part of the family, you're part of it for good.