You can get away with a lot when it comes to casting. Sometimes, certain things like historical accuracy (in the case of biopics) or faithfulness to the source material (when it comes to comic book movies or remakes) can be overlooked if an actor is right for the part. Even if bold casting choices cause backlash, sometimes, if the person's right for the role, then that's all that matters.
One way casting can be forgivably implausible is when it comes to casting one actor as a parent, whilst the actor playing their child is almost the same age. This has happened many times throughout film history, and the following films are some of the best examples of huge age gaps in casting characters who were supposed to be born a generation apart.
'North by Northwest' (1959) - Jessie Royce Landis & Cary Grant
Northwest by Northwest is one of the finest thrillers Alfred Hitchcock ever directed. While he made numerous films that featured a person on the run after being mistaken for someone they're not, this is probably the best of them, with it remaining a fast-paced, entertaining film over 60 years on from its release.
It's a good enough movie that you don't even mind the fact the lead role was probably written with someone younger than Cary Grant in mind. Make no mistake, he's still fantastic in the role, but when he's paired in a romance with Eva Marie Saint (20 years his junior), and with his mother being played by Jessie Royce Landis (only eight years older than him!), you can't help but notice his age a little.
'The Graduate' (1967) - Anne Bancroft & Katharine Ross
An important and daring film for the year it came out, The Graduate tells the story of a young man, fresh out of college, struggling with what to do for the remainder of his adult life. Part of his confusion stems from the affair he has with Mrs. Robinson, who's many years older than him, and the mother of the young woman his parents want him to date, Elaine Robinson.
Mrs. Robinson is played by Anne Bancroft, who was born in 1931, while Elaine is played by Katharine Ross, who was born in 1940. Still, the difference isn't too jarring, as Ross successfully plays a few years younger than her age, and Bancroft successfully pulls off playing a few years older, but the gap between their ages is still pretty narrow.
'The Manchurian Candidate' (1962) - Angela Lansbury & Laurence Harvey
A political thriller about conspiracies, paranoia, and assassinations, The Manchurian Candidate is a classic 1962 film that was remade in 2004. Laurence Harvey, then 34, plays Shaw, a man whose life is hijacked when he becomes brainwashed into becoming an assassin. His mother is played by Angela Lansbury who was 37 - only three years Harvey's senior - at the time the film was released.
It works well enough, thanks to Lansbury really disappearing into the role and convincingly playing a good decade or two above her actual age. Sure, it's not the most realistic casting, but the movie holds up well and is something of a classic, so the decision to cast the two worked out in the end.
'The Northman' (2022) - Nicole Kidman & Alexander Skarsgård
Demonstrating that big age gaps between actors playing parents and children are not confined only to old Hollywood movies, 2022's dark and violent revenge epic, The Northman, also provides an example of this phenomenon.
Alexander Skarsgård (born 1976) plays the film's main character, Amleth, who wants to seek vengeance for his father's death and rescue his mother, played by Nicole Kidman (born 1967) from his father's murderer. While not the most egregious example of an age gap, it's still less than a decade and becomes astounding when you remember that Skarsgård and Kidman had previously played husband and wife (in the TV show Big Little Lies).
'Alexander' (2004) - Angelina Jolie & Colin Farrell
A somewhat forgotten historical epic about Alexander the Great, 2004's Alexander contains one of the most dramatic instances of an age gap between fictional parent and child. Angelina Jolie (born in 1975) is only one year older than Colin Farrell (born in 1976)... yet in the film, she plays his mother.
This is a particularly jarring example because little is done to make Jolie look older, and similarly little is done to make Farrell look younger. It would make far more sense for the two to play siblings, but for whatever reason, they were cast as two real-life historical figures who in actuality were born about 19 years apart.
'Scarface' (1983) - Míriam Colón & Al Pacino
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A classic Brian De Palma film that stars Al Pacino at his most explosive, Scarface has an enduring legacy of being one of the most iconic crime films of all time. It's a classic rise-and-fall story about an ambitious, ruthless gangster who builds an empire, only to see it crumble around him.
While Tony Montana's sister is a prominent character, there are also a couple of scenes featuring Tony's mother. Pacino was only four years younger than Míriam Colón, who played his mother. If you accept Tony as being a good 10 years younger than Pacino, it's not too hard to buy, but either way, it's obviously way too close for them to be parents in real life.
'Mrs. Miniver' (1942) - Greer Garson & Richard Ney
A classic World War 2 drama about a family surviving constant air raids in England during the war's early years, Mrs. Miniver is notable for being made right in the middle of the war, with its aim to reflect the times and give everyday people some catharsis (and a little hope) during a dark period in history.
Beyond its historical significance, it's also notable for having the title character, who's played by Greer Garson (born 1904) have a son played by an actor who was only 12 years younger than her (Richard Ney). Sure, the over 10 years difference is better than under at least, but this example is worth bringing up for the fact that shortly after they filmed Mrs. Miniver, Garson and Ney got married in real life, and were together between 1943 and 1947.
'Blow' (2001) - Rachel Griffiths/Ray Liotta & Johnny Depp
This biographical film about a drug dealer in the 1970s provides a two-for-one deal when it comes to parent-child age gaps. Johnny Depp was 38 in the year of the film's release, while the late Ray Liotta (who played his father) was 47, and Rachel Griffiths (who played his mother) was 33 in 2001... five years Depp's junior.
It's surprising enough to have two parents be played by actors of a similar age, but to have one be younger than their supposed on-screen child is something else. Granted, many scenes with Griffiths and Liotta center on flashbacks, when Depp's character is played by a younger actor, but they do share the screen with Depp at some points, too.
'Tommy' (1975) - Ann-Margaret & Roger Daltrey
An ambitious and wild rock opera musical that features no traditional/spoken dialogue, Tommy is essentially a feature film adaptation of The Who's album of the same name. It's about a boy who grows into a man, along the way losing and regaining his sense, becoming a pinball expert, and starting a cult. It makes a little more sense in context, but only just.
The title character is played by The Who's lead singer, Roger Daltrey, while his mother is played by Ann-Margaret. The former was born in 1944, whilst the latter was born in 1941. You can kind of tell they're of a similar age in the film, but then again, there's also so much weird stuff going on you could well be too distracted by other strange things to notice.
'Giant' (1956) - Elizabeth Taylor & Carroll Baker/Dennis Hopper
An epic family drama with a huge cast and runtime (well over three hours!), Giant spans many years and stars a young Elizabeth Taylor. Naturally, given the decades worth of story, her "children" end up being her age, with some make-up used to make it less jarring.
The effects are far from seamless, but it's an older movie, so it's more forgivable. Still, the fact she has two improbably aged kids does make it an extra humorous example of this sort of casting. Taylor was born in 1932, while Dennis Hopper, who played her son, was born in 1936, and even more surprisingly, Carroll Baker - playing Taylor's daughter - was born in 1931!