I love the animated show, it's actually my favourite thing Gervais has ever done. Is Karl a character? Maybe he is, maybe he isn't. Regardless, he's fucking comical. You're quite gullible if you don't realise that, like wrestling, most entertainers that are entertaining are playing an exaggerated form of themselves. What's wrong with that? Everyone in media/entertainment is very different on camera or over the radio. Do you think a stand-up comedian is the exact same on and off stage?
He might play it up for the show/s but I don't think that should be an issue.
What DOES annoy me during the show, sometimes, is Gervais jumping down Karl's throat and interrupting him. Sometimes it works and adds to the comedy and other times you just want him to shut the fuck up and wait for Karl's next gem.