The crossover stuff really appeals to me, like how in Curb Your Enthusiasm Larry David and Ted Danson play versions of themselves and are friends, while in Seinfeld when they were developing the pilot for the show-within-a-show, George would draw these comparisons to Ted Danson and expect to be treated that well even though this was his first break in showbusiness.
I actually liked the finale for Seinfeld and the way Larry David wrote that, but so many people hated it that the finale for Curb Your Enthusiasm was even funnier, I thought.