I've got to say that since this thread has resurfaced, I've totally changed my opinion, I think Karl Pilkington is hilarious and he's definatly not fake.
Parts of An Idiot Abroad had me in stitches and since then I've been listening to all the podcasts (which I missed at the time) along with the animated Ricky Gervais Show and the archive of XFM Shows. I can't get enough of it!
It's when you listen to the early XFM Shows when he was just Producer that you realize he isn't a fake character, because they put a question to him and it's obvious he isn't very comfortable talking on the radio as he is the Producer and not one of the Presenters. It's only because his responses were so ridiculous that they began including him properly in the show because they knew how hilarious he would be.
Perhaps they play it up a little more now that there is a lot of money involved from the likes of Sky and HBO, but he is still quite genuine I think.
It actually made me think that I once knew somebody who was like Karl. He always had a story to tell and he was hilarious without intending to be funny. I think more than anything it was down to him being incredibly gullible, which I think Karl also suffers from, believing what he has been told or read.
Rumor has it that the next series they do for Sky will be called 'The Bucket List' and will feature Karl doing all the things that say you should do in your life before you kick the bucket.