Oh, he's a complete Who geek. I've not listened to all the commentaries, but on the ones I have, he'll just throw something into the conversation - not as a name-dropping exercise or a 'look at me' thing, just some Who fact or other that he feels is relevant, and you can tell it's completely 'natural'.

He's also a huge fan of my "other" show, The West Wing - so clearly he tends towards fanboyishness in general :-)