The tattoo on the shark was a joke by the crew. Of course, once it made it into the show, then it's continuity and Must Be Explained/able.

For two other examples of the Nerd Axis:

* David Lynch. I spent more time talking about Mulholland Drive than I did watching it, and Twin Peaks is... just... well... yeah.

* The Legion of Super-Heroes. 50 years old as of two weeks ago, with five distinct major continuities (maybe 6; includes a cartoon show with its own comic, so there are three conflicting continuities being published right now every month!), and fans who track each, have favorites, and can mutually explain all discrepancies. Requires being able to quickly establish a mental matrix of 20-30 character names, real names, superpower sets, and home planets, plus relationships between them. (Most of which are the same in each continuity. Except the ones which are not.)