The "National Lampoon's Vacation" franchise includes a total of five main films: 1. **National Lampoon's Vacation** (1983) 2. **National Lampoon's European Vacation** (1985) 3. **National Lampoon's Christmas Vacation** (1989) 4. **Vegas Vacation** (1997) 5. **Vacation** (2015), which serves as a sequel and a reboot. Additionally, there are several spin-offs and related films, but these five are the primary ones in the original series.

One of the most famous lines from "National Lampoon's Christmas Vacation" is Clark Griswold's enthusiastic declaration, "It's Christmas! We're all in this together!" This line captures the chaotic yet festive spirit of the holiday season as Clark tries to create the perfect Christmas for his family. The film, released in 1989, is a beloved holiday classic known for its humor and memorable moments, including Clark's iconic Christmas lights display and the mishaps that ensue throughout the story.

In "National Lampoon's Vacation" and its sequels, the Griswold kids, Rusty and Audrey, are portrayed by different actors in nearly every film due to the passage of time and the aging of the characters. This casting choice reflects the natural aging process and allows each movie to present the kids at different stages of their lives. The first film, released in 1983, featured Anthony Michael Hall as Rusty and Dana Barron as Audrey, while later installments showcased different actors, such as Jason Lively and Marisol Nichols, in those roles.

As of my last update, "National Lampoon's Vacation" is not available on Netflix. Streaming availability can change frequently, so it's a good idea to check Netflix directly or use a service like JustWatch to see if it has been added or is available on other platforms.