Hollywood has been casting adults to play teenagers since the dawn of time. Some of these actors fit the bill, but some of them looked wildly out of place in their roles, especially when compared to how they *actually* looked during their high school years.

1.The late and great Olivia Newton-John was a decade older than her character Sandy — a high school senior — when she filmed the iconic Grease movie.

Here's what Olivia Newton-John (left) actually looked like at 18 years old, circa 1966.

2.Leonardo DiCaprio got away with playing a teenager in Catch Me If You Can when he was 28. Of course, that can be credited to his charming "baby face" at the time.

Leo has never looked his age, even as a teenager. This was him at 17 years old.

3.At 26, Minka Kelly starred as 16-year-old Lyla Garrity on Friday Night Lights.

Here's a video montage that Kelly posted after reuniting with one of her high school best friends. The clip features several nostalgic photos of the pair during their teenage years.

4.Ross Butler played 17-year-old Zach Dempsey in 13 Reasons Why when he was 26 years old. He also briefly played a teenaged Reggie Mantle on Riverdale before Charles Melton took over the role for Season 2.

And this is how he actually looked throughout his high school years.

5.Troian Bellisario was 24 while playing 16-year-old Spencer on Pretty Little Liars.

And this was Troian during her early teen years, proudly displaying her science fair trophy.

6.This is how Cole Sprouse looked while playing a teenaged Jughead Jones on Riverdale.

...And this is how Cole Sprouse really looked as a teenager. Fascinating stuff.

7.Lucy Hale wasn't drastically older than her Pretty Little Liars character. She was 20 years old while playing 16-year-old Aria.

This was Hale when she was actually in high school.

8.Bianca Lawson was 31(!) while playing 16-year-old Maya on Pretty Little Liars.

Bianca spent her real-life teenage years appearing on shows like Saved by the Bell and Sister, Sister.

9.27-year-old Ben Platt sadly couldn't pass as a convincing high schooler in the Dear Evan Hansen film.

This is what he really looked like in his late teens.

10.Ashley Benson wasn't much older than 16-year-old Hanna while filming Pretty Little Liars, though she was still an adult playing a teenager. She was 20 years old when she got cast in the popular series.

Here's what Benson looked like when she was the same age as Hanna.

11.The ever youthful Gabrielle Union got away with playing high school cheerleader Isis at the age of 26 in Bring It On.

This was Gabrielle during her real-life school years, every bit as athletic.

12.You'd never guess it, but Asa Butterfield was 24 when he started playing 17-year-old Otis on Sex Education. His boyish appearance definitely works in his favor.

This was Asa Butterfield at 16. Not much has changed.

13.Ryan Phillippe was 25 when he starred as a high schooler in 1999's Cruel Intentions.

And this is how Ryan Phillippe looked at 18. A little more innocent and a little more charming, but he was always a good-looking guy.

14.As its title implies, some of the characters in The Vampire Diaries are...vampires. That said, Paul Wesley's Stefan Salvatore is supposed to be forever 18, though the actor was 27 years old when he got cast.

These are some photos of Wesley during his teenage years.

15.Nina Dobrev was 20 years old when she was cast to play 17-year-old Elena Gilbert on The Vampire Diaries.

This was Dobrev as a teenager, just two years before joining TVD.