What happened to Hitchcock's navel then HC? - seems very odd, how was he attached? :-/ :-/
Hitchcock, like everyone else, was born with a navel. Supposedly, he had a small section of his belly that contained the navel removed during some sort of surgery. This, I gather, is not that uncommon.
Apparently ...All mammals except platypusses (platypi?) and echidnas have a belly-button equivalent, where their umbilical cords were attached to their placentas - with cats and dogs and such, it just looks like a flat scar. In humans, it's attached by ligaments to the abdominal wall muscle and surrounded by fat so it makes a noticeable dimple. Unless lopped off by an enthusiastic surgeon 
How do you know all this stuff HC?
The main disadvantave that I can see with such an absence is, where would all the fluff accumulate? :-/ :-/ 
Ah -- now, the obvious alternative would be the little dimple at the base of the spine ..... you know the one!?
The burning question, slightly off the topic, is why is this fluff always blue !?