why is it called national lampoon's christmas vacation

The movie is called "National Lampoon's Christmas Vacation" because it's based on a series of National Lampoon magazine articles that were written by John Hughes in the 1980s. The articles were about a family named the Griswolds who were trying to have the perfect Christmas but kept running into mishaps and misfortunes. The movie was adapted from these articles and became a beloved Christmas classic, but the original articles were actually pretty dark and cynical. So, the movie is called "National Lampoon's Christmas Vacation" because it's a parody of the original articles.