Christopher Guest knows about "mockumentary" films. I mean, come on, he was Nigel Tufnel in Spinal Tap! So I guess it wasn't a big shock when he directed his own faux documentary in 1996, Waiting for Guffman. He (along with much of the Guffman cast) followed that up in 2000 with Best in Show.
Guest has said he doesn't like the term "mockumentary," because he doesn't mock the characters in his movies. He has a point. Even when his characters might be deserving of mocking (Best is about people who take dog shows a little too seriously), he manages to find some humanity in each of them. I'd guess he also probably understands that everyone has an obsession or two that others find odd (or flat-out silly).
Best was filmed without a traditional script. Guest relied on his talented cast to improvise all the movie's dialog, and each actor comes through brilliantly. In fact, the Best DVD contains more than an hour of improv material that didn't make the final cut, and these guys' "B" material is better than most actors' grade-A stuff.
Honorable Mention: A Mighty Wind
In A Mighty Wind, his 2003 follow-up to Best, Guest spends as much time developing interesting characters as he does developing jokes. But the movie still has plenty of moments of comedic genius. And plenty of great songs. Wind is about the folk music scene, and the original songs written for the film manage to both pay tribute to and poke gentle fun at the great folk music of the past.
Tomorrow: "For relaxing times, make it Suntory time."