It recently won the American Comedy Award for Best Comedy Film, and deservedly so.
If you've seen Guest's previous work -- Waiting for Guffman -- or his involvement in Spinal Tap, you'll get the joke. This is a largely improvised movie about people bringing their dogs to the dog show, with the hopes that their pooch will be named BEST IN SHOW.
We fololw Harland Pepper (Christopher Guest) and his bloodhound. Gerry and Cookie Fleck (Eugene Levy, Catherine O'Hara) and their dog. Michael Hitchcock and Parker Posey play *very high strung* dog-owners. Michael McKean and John Michael Higgins play a gay couple with their dog. There's also an older guy, his trophy wife and their lesbian dog trainer none of whose names ring a bell right now.
Fred Willard shows up at the dog show to provide some ha!-sterical commentary.
Do yourself a favor and whet your appetite with the unused scenes over at their site: BestInShowOnline.com
Funny funny stuff.
I am trying not to give too much away. :-)

