RACHEL MARTIN, HOST:

And while you are chugging your mead, how about watching a classic holiday movie? What's the best one, do you think - "Miracle On 34th Street," "It's A Wonderful Life," "A Christmas Carol" - no, "National Lampoon's Christmas Vacation," of course.

(SOUNDBITE OF MOVIE, "NATIONAL LAMPOON'S CHRISTMAS VACATION")

CHEVY CHASE: (As Clark Griswold) Two hundred fifty strands of lights, 100 individual bulbs per strand, for a grand total of 25,000 imported Italian twinkle lights.

UNIDENTIFIED GROUP #1: Yay.

MARTIN: Twenty five years ago this month, Chevy Chase starred as Clark Griswold in this third film from the National Lampoon Vacation franchise. Mental Floss has chosen to mark this hallowed anniversary by noting some choice Christmas Vacation tidbits.

Among them, writer John Hughes of "Breakfast Club" fame based the film on a short story he first wrote for National Lampoon magazine in 1980. Continuity was not key between these movies. While son Rusty Griswold was sister Audrey's older brother in the first two vacation flicks, he is transformed into the younger sibling come Christmastime 1989. And in every Vacation movie, the kids are played by different actors. Finally, "Christmas Vacation" is that only sequel to have its own sequel. In 2003, "National Lampoon's Christmas Vacation 2: Cousin Eddie's Island Adventure" debuted. Maybe it's too soon to call that one a holiday classic. Transcript provided by NPR, Copyright NPR.