"Best In Show", "Waiting For Guffman", "A Mighty Wind", "This Is Spinal Tap" are hilarious movies, but they're scripted movies with great professional actors. They're called "mockumentaries".
The "Pursuit of Excellence" series, especially Ferrets, are all pure, legit documentaries, entirely unscripted with real-world, natural nuts. I laughed so hard my ribs were sore.