I didn’t realize that either until last week (see post 17). I though “Rusty” looked a lot like a young Leonard Hofstadter so I had to look it up on IMD to be sure. But if I am not mistaken, every “Vacation” movie had different actors in the roles of the Griswald kids, Audrey and Rusty. Johnny Galecki while not particularly a stand out in the role of Rusty in Christmas Vacation has probably had the most commercial success post “Vacation”. The only actors to reprise their roles outside of Chevy Chase and Beverly DeAngelo are Randy Quaid and Miriam Flynn as Cousin Eddie and Catherine.