The Vacation movies have their share of running jokes, be it Clark's adulterous fantasies or Cousin Eddie's many disgusting physical ailments. But one thing that remains consistent throughout the films is the maddening inconsistency of the young actors who play Griswold kids Rusty and Audrey and their many bizarre cousins.

Not only do the actors change from film to film -- the characters' ages flucuate as well. (Rusty goes from pre-teen to teen and back to being a kid over the course of three movies.) Do the Vacation movies exist in some sort of perpetual time loop? Does the entire franchise take place in Clark's head, a fever dream of a perfect family vacation where his kids never fully grow up? Or can the frequent cast changes be chalked up to the whims of whatever screenwriter is in charge of the franchise at the time?

Whatever the reason, the Vacation movies have given us a plethora of young actors of varying quality. Before you watch the first Vacation movie on IFC, take a look at our definitive ranking of every kid from the long-running franchise.

12. Rusty #2 (Jason Lively), European Vacation

http://youtu.be/cF_OdUF8lzo

For the second Vacation outing, Rusty went from a wisecracking kid to a horny teenager straight out of a generic Porky's rip-off. He's quite possibly the single most annoying character in the entire Vacation franchise, which is quite a feat. He's even lame in his own dream sequence, where he wears a ridiculous white suit with his name written on the back. (Fun fact: Jason Lively comes from an acting brood -- his brother Eric was on The L Word and his sisters are Robin "Teen Witch" Lively and the most famous family member, Blake Lively.)

11. Rocky (Cody Burger), Christmas Vacation 

http://youtu.be/KFoqhey_eCA

Cousin Dale, Eddie's son from Vacation who talks about his dad's "asteroids," has suddenly been replaced by young Rocky by the time Christmas Vacation rolls around. Only Rocky doesn't say a word during the entire movie. (Considering that Eddie is his dad, he's likely traumatized.) Still, he has a pretty sweet mullet, which gives mute lil' Rocky an edge over Rusty #2.

10. Audrey #2 (Dana Hill), European Vacation

http://youtu.be/-YHDL8vOg8A

Audrey's body issues are a source of constant ridicule in the lackluster Vacation sequel. (She's basically the Meg Griffin of the series.) When she's not having horribly offensive fantasies about being stuffed with French pastries, Second Audrey is ignoring the European sights and whining about missing her lunkhead boyfriend. She's basically every teenage girl stereotype in one grating package.

9. Audrey #4 (Marisol Nichols), Vegas Vacation

http://youtu.be/bSY8UUOT-Ak

Like the sequel that she appears in, Nichols (24) is pretty forgettable. Again, Audrey's age here is a problem. If Audrey was 15 or 16 in 1989's Christmas Vacation, that would put her in her mid-twenties by the time 1997's Vegas Vacation came out. But somehow she's back to being 16 again. Clearly Clark has some sort of de-aging machine that keeps his kids from being too old to be dragged on wacky family vacations. 

8. Rusty #4 (Ethan Embry), Vegas Vacation

http://youtu.be/Ng5V1p6tPRU

Embry would go on to play likeable goofballs in films like Can't Hardly Wait and Sweet Home Alabama. But here he's stuck playing another variation on "horny Rusty." Only this time he goes by the smooth alter ego "Nick Papagiorgio."

7. Cousin Vicki #1 (Jane Krakowski), Vacation 

http://youtu.be/AOXQTr_3IVw

We can't help but see hints of Jenna Maroney in Krakowski's big screen debut as Cousin Eddie's oldest daughter. We also can't help but cringe now at the line about how daddy says she's the best French kisser in her class.

6. Cousin Vicki #2 (Shae D'Lyn), Vegas Vacation

http://youtu.be/beWjk_Q6yZ4?t=2m53s

With a father like Eddie, it's no wonder that Vicki grew up to be a stripper who shows Audrey the Vegas nightlife.

5. Ruby Sue (Ellen Hamilton Latzen), Christmas Vacation

http://youtu.be/mmSagEecXtU

On the scale of precocious kids from John Hughes movies, Ruby Sue falls somewhere between Curly Sue and Gaby Hoffman's character from Uncle Buck -- cute in a ragamuffin sort of way, but mostly forgettable. (Ruby Sue turns up again in Vegas Vacation, naturally played by a different young actor.)

4. Original Audrey (Dana Barron), Vacation and Christmas Vacation 2: Cousin Eddie's Island Adventure

http://youtu.be/wPfIc21S2Q0

Barron gets points for being the original Audrey and also for being the only Griswold kid to reprise her role. Granted, she came back as the grown-up Dana in the unwatchable TV movie Christmas Vacation sequel.

3. Audrey #3 (Juliette Lewis), Christmas Vacation

http://youtu.be/0ar-__ub0rc?t=3m23s

Juliette Lewis scored one of her first movie roles as the easily embarrassed teenage Audrey in Christmas Vacation. Lewis nicely underplays the role, making her easily the least annoying Audrey in the franchise.

2. Original Rusty (Anthony Michael Hall), Vacation

http://youtu.be/iYTdILs7-1Q

Anthony Michael Hall's rising fame (he opted for Weird Science instead of the Vacation sequel) led to the Griswold kids getting recast for each subsequent installment. But that doesn't explain their fluctuating ages.

1. Rusty #3 (Johnny Galecki), Christmas Vacation

http://youtu.be/q-YcvJJt-WA

The future Big Bang Theory star gets the nod for best -- and least irritating -- Griswold kid. His deadpan reactions to pop Clark prove that young Galecki had comedic chops even before his breakthrough role on Roseanne.