#1 Thomas Brodie-Sangster Was Actually 14 When He Played A 7-Year-Old Kid In Nanny Mcphee

#2 Laurence Fishburne Was Only 14 When He Played A Soldier In Apocalypse Now

#3 Shirley Henderson, Who Played Moaning Myrtle In The Harry Potter Films, Was Actually 37 When She Appeared In The Second Film

If you wonder why so many teenage roles are actually played by adult actors, there may be a good reason or two for this. First of all, according to child labor laws, kids can only work for up to a few hours at a time. Meanwhile, movie sets and TV productions will normally spend 10-12 hours a day working on a set.
There is also the issue of schooling that most minors are still required to complete. Plus, minors are more expensive to get insured if their job requires them to do stunts and physical work. Casting slightly older actors may be a workaround for not paying extra costs.
Moreover, the child actor can outgrow the age of their characters as their aging is more noticeable. Think of the ages 13 and 18 and how vast the difference is. And lastly, the great majority of professional actors are twenty and up, so they always already have greater experience and acting skills to compare with teenage and child actors.
#4 Audrey Hepburn 32 In Breakfast At Tiffany’s As 18 Year Old

#5 John Franklin, Children Of The Corn. The Role Of The 12-Year-Old Prophet In The Horror Movie Children Of The Corn Became A Debut For John Franklin. By That Time The Actor Had Already Turned 25

#6 Winona Ryder Was 28 When She Played An 18-Year-Old In "Girl, Interrupted" As Susanna Kaysen

For many child actors who start out at a very early age, the sudden fame and intense work load may be debilitating. Macaulay Culkin, who started acting at the age of 4 and got famous for his role as Kevin McCallister in the Home Alone films, has said multiple times how truly hard it all was.
“It started feeling like a chore. I started vocalizing that and not being heard: I was saying, ‘I wanna go to school—I haven’t done a full year of school since first grade,'” he told Esquire in a recent interview.
Culkin’s lifelong struggle with psychological problems also serves as an example that casting a very young actor for a leading role which requires a lot of responsibility may be, in some way, harmful.
#7 Amanda Seyfried Was 27 When She Played The Teenage Cosette In Les Misérables

#8 Keiko Agena Played A 17-Year-Old Lane In Gilmore Girls While Being 27-Years-Old

#9 Olivia Newton-John - 28 In Grease As Sandy Dumbrowski - 17

#10 Jack Gleeson, 25, As King Joffrey In Got, 17. In The Books He Was Only 13-Years-Old

#11 Alan Ruck - 30 In Ferris Bueller's Day Off As Cameron Frye - 18

#12 Keanu Reeves, Bill & Ted’s Excellent Adventure. He Played A 17-Year-Old Schoolboy At The Age Of 25 In The Sci-Fi Comedy Of 1989

#13 Sophie Mcshera Plays The Young Kitchen Maid Daisy In "Downton Abbey" While Being 35-Years-Old

#14 Michael J. Fox - 29 In Back To The Future As Marty Mcfly - 17

#15 Cole Sprouse Is 27 Years Old, But His "Riverdale" Character Jughead Is Meant To Be Just 16

#16 Jon Heder - 25, Napoleon Dynamite - 16. He Certainly Knew How To Act Like A Teenager

#17 Jennifer Grey - 27 In Dirty Dancing As Frances “Baby” Houseman - 17

#18 Leonardo Dicaprio - 28 In Catch Me If You Can As Frank Abignale Jr. - 16

#19 Ian Somerhalder Started Playing Damon Salvatore, A Vampire Turned-At-25 When The Actor Was 30-Years-Old And Finished The Show When He Was 38-Years-Old Still Playing A 25-Year-Old

#20 Kit Harington Was 30-Years-Old While Jon Snow Is Supposed To Be 17. In The Books He Was 14



