The Kranks are (initially) planning to skip Christmas this year, which means their demand for Christmas trees decreases. When their daughter announces that she’ll be back home for Christmas, the Kranks scramble to try and find a tree. Unfortunately for Luther, there aren’t many trees available because it’s so close to the holidays and he ends up paying full price (instead of a discounted price) for a pathetic tree. When decision-makers don’t have much time to make a purchase (like Luther right before Christmas), their demand is fairly inelastic.
Thanks to Mandy Mandzik for the clip recommendation. Check out her working paper, All I Want for Christmas is an A on My Econ Final: A Holiday-Themed Review Class, for more Christmas-themed economics examples.