Everyone has a different get-off-my-lawn moment, a fact that makes them suddenly feel their age. And the entertainment world, with all its unnaturally young-looking senior citizens and overly made-up kids, supplies more than its share of such realizations.
Maybe it's the fact that Ralph Macchio, who played Daniel-san in the original "Karate Kid," is now the same age as Pat Morita was when he played Mr. Miyagi. (Thanks, Yahoo and Roadside Attractions for that little day-brightener.) How in the name of Cobra Kai did this happen? Weren't they just waxing on and waxing off yesterday?
Or the fact that if Andie and Blane (or, as we prefer, Andie and Duckie) had stayed together after the 1986 film "Pretty in Pink," they could have adult kids or even grandkids by now.
Here are some more blasts from the "do-you-feel-old-yet?" department.
He's really 'Big'
Josh, the 12-year-old kid who turned into a 30-year-old in 1988's "Big," would be 37 by now.
He'll forever be a school-age wizard in our minds, but according to some geek math, Harry Potter would be either 33 or 34 today.
Ferris Bueller would be celebrating either his 26th or 27th high-school reunion. He's now older than Ben Stein was when Stein played the droning economics teacher who famously called "Bueller ... Bueller." (Still a righteous dude.) Want to feel even older? Alan Ruck, who was 29 when he played 18-year-old Cameron, is now 56.
Assuming Maggie, Bart and Lisa were 1, 10 and 8 when "The Simpsons" began, they'd now be 24, 34, and 32.
The twins born to Chandler and Monica's surrogate mother on the "Friends" finale would be 9. Ross' son with Carol, Ben, would be 19, and his daughter Emma, with Rachel, would be 11.
'Fast Times' indeed
Sean Penn, who played high-school senior Jeff Spicoli in 1982's "Fast Times at Ridgemont High," is now 52.
John Travolta, who played Sweathog Vinny Barbarino on "Welcome Back, Kotter," is 59 -- almost twice as old as Gabe Kaplan was when he played Barbarino's teacher, Gabe Kotter, and three years older than John Sylvester White was when he played crotchety assisstant principal Mr. Woodman.
Smells like twentysomething spirit
The baby on the Nirvana "Nevermind" album cover, Spencer Elden, is now 21.
One doodle that can't be un-did, homeskillet
The baby born to Juno in the 2007 movie "Juno" would be preparing for kindergarten.
Randee Dawn contributed to this story.