Ah yes. Dawson casting. The phenomena of casting actors older or younger than their characters, and the age difference is noticeable.
Examples of justified Dawson casting are rare. By justified, I mean within the context of the film/show, not because of other factors, since 16 year olds are minor and its easier to get a 24 year old.
The only example that I can think of is in the Lovely Bones movie where
the main character’s sister is a year younger than her while the actress who pays said younger sister is 8 years older. The main character dies at 14 and is a ghost throughout the film, but her sister grows older in a film whose timeline is nearly a decade long and thus was necessary
Well, your OP seems to be kind of not what you’re looking for (casting older for ease in filming, not for story reasons) but often they either age characters from books or hire older actors because of the adult situations the characters will be portrayed in. (They’re aging all the kids up in A Game of Thrones, I think, probably for a number of reasons but that’s sure to be one of them.)
Cameron (Summer Glau) in Terminator: The Sarah Connor Chronicles. Glau was 27-28 when she played the “teenage” Terminator, but the show later explained this in a pretty smart way. In one episode Cameron gets a job at a nuclear power plant and is served alcohol in a bar with a fake ID. So the show establishes that she’s not supposed to be a teenager anymore than she’s supposed to be a woman in her mid-20s. Later still, we meet the human woman Cameron was based on and she was 21 at the time of copying (but living in the burned out post-Judgment Day, which will obviously age you prematurely).
Hiring older actors due to legal issues is not what the OP is looking for.
On the other hand hiring older actors since for example the character ages through the film is ONE of the examples where it is justified. So in the OP example
[spoiler] having an older actress playing the role of a ghosts younger sister was justified since she grew older unlike the ghosts.
In the UK’s execrable (ETA: yet very addictive) high school soap Waterloo Road, jailbait Jess is meant to be 16 or 17, but is actually played by a 23-year-old. That’s not for legal reasons as far as I can tell, since many of the actors she plays against are indeed the same age as their characters.
I should have added, I think the justification in casting is that she needs to exude a sexuality and worldliness that would probably not be present in younger actresses.
How about the Harry Potter franchise?
The timeline of the books covers 7 years, but the film series is taking considerably longer to film (I’m wanting to say 10 years? But I could be off +/- 1)
Now the main characters were very slightly older-ish looking in the first few films, because they didn’t actually use 10-year-olds (I think Daniel Radcliffe was 13, Emma Watson was 12?) – but by now, in the final films, it’s getting to be laughable to cast them as teen-agers. Yet you couldn’t very well switch them mid-stream, either…
I remember reading a few years back that the original plan was to switch out all the main actors either before or after Goblet of Fire but the producers realized that would be stupid because fans had grown attached to the three.
I’m not sure it’s a spoiler to mention that she was 24 playing a 14-year old in the movie. What happens later, sure, but not her age.
Cold Case usually needed to portray characters both in the present and years (or decades) younger in flashbacks. I don’t have any specific examples but it seems like, for the shorter jumps, makeup and soft focus would be easier than finding two actors with enough resemblance to play the same person.
The movie Grease cast the seniors at Rydell with older actors because the director wanted them to stand out from the real teenagers used as the underclassmen extras. The idea was that the seniors would look more ‘grown up’ next to the extras and bring home the idea that these were people ready to leave childhood behind and move on as adults at the end of the year (ie. Kinickie and Rizzo getting married).
In the musical Gypsy, which was also rendered on TV and film, Louise aka Gypsy Rose Lee ages from about 10 to about her mid-20s. In all the versions I’ve seen, “Baby Louise” is cast with a child actor, but the older versions (young teenager to adult) are played by the same woman. It makes sense to cast for the older end of the range, as otherwise you’ve got a teenager playing a burlesque star.
On the BBC/HBO series Rome, Max Pirkis played Octavian during the first season (and I think a bit during the second season). I think he was around 15-16 during the first season, but the character aged from around 11-12 (although his exact age wasn’t clear) in the first episode to around 20 or so (again, the exact age wasn’t clear) in his last appearance. After that, the character was played by a different actor.
In Absolutely Fabulous, Julia Sawalha played the lead character’s 16-year-old daughter Saffron, despite being seven or eight years old than her character, and only ten years younger than Jennifer Saunders, who played her mother.
It’s justified because Saffron is supposed to be the mature voice of reason way older than her years, so getting somebody actually older than 16 makes sense, as long as they can pull it off, which I think she did.