A marvelous series ... nary a lame episode in the lot and lots of bored-pilots-in-the-cockpit games to play! And there's no other place in time, space, fact, or fiction where the line "No, I'm sorry, Carolyn. I carried the sheep for you. I climbed the tree. I rode in the back of the truck. But now, I need to X-ray these geese." makes perfect sense.
Edited to add: Creator/scriptwriter/cast member John Finnemore's own words on the subject (And now I have to add his blog to my online reading list because the most recent entries on G.K. Chesterton and Winston Churchill were wonderful)