When Springfield had a film festival in 'The Simpsons', and when Bart's football team hosted the team from Arlen, Texas, animation styles were mixed with the guest appearances by Jay Sherman of 'The Critic' and Hank Hill's family from 'The King Of The Hill', respectively.
That's pretty much all the info I have so far. Gervais wasn't very forthcoming in his blog:
"I won't give the joke away but they are featuring a little clip of The Ricky Gervais Show in a future episode."
So stay tooned!
Sorry about that, Chief......