There has been a flurry of “gender-swapping” in movies lately. In particular, women are now playing superheroes and more active roles in action films – roles that would formerly have been taken by men.

The most obvious example is the recent Ghostbusters movie, in which the heroes played in the original 1984 film by Bill Murray, Dan Aykroyd, Harold Ramis, and Ernie Hudson were in 2016 reenvisioned and played by Melissa McCarthy, Kristen Wiig, Kate McKinnon, and Leslie Jones.

(It’s beside the point whether the film should have been remade, when the original film is now a classic and was nearly perfect just the way it was. I hate movies that are treated like that: See Bedazzled, Psycho, Ben-Hur, The Pink Panther.… but I digress.)

Action and comedy films seem to be the usual targets of this treatment, and there’s a reason for that. Action and broad comedy are at heart fantasy movies, about things that could never happen in the real world. When you’ve got things that can’t happen anyway, the gender of the person they can’t happen to is largely irrelevant.

But let’s take a look at a more “serious” fantasy movie – Field of Dreams. To recap briefly, the story involves an Iowa farmer who is suddenly compelled to build a full-size baseball field on his property so that the ghosts of a baseball team can play out their redemption. There is a small part for a female, who gets one incidental subplot as an activist at a school board meeting. But her main role is to be supportive and say things like, “I don’t know, honey,” but quickly come around to enabling his ridiculous dream, even though it means nearly losing their home and land.

It was a wildly popular movie, especially with men and baseball fans.

And it could never be gender-swapped.

Imagine a film in which a wife has a crazy fantasy dream that requires giving up everything the couple has been working for all their lives, with no guarantee of ever getting it back. Now imagine that the husband stands steadfastly by, encourages her, signs the mortgage papers, and supports not simply her decisions, but her fantastic delusions.

You can’t do it. The movie couldn’t be made. No one could write it and make it believable (even within the parameters of a basically unbelievable plot).

A man with a crazy dream is an underdog hero who deserves a stand-by-your-man woman. A woman with a crazy dream is – just crazy. She wouldn’t get past turning under the first crop before being carted off for psychiatric help. At some point in the movie, divorce would ensue.

Of course there are women in real life who accomplish great things and men who support and encourage them – take Amelia Earhart, for example. But these are different situations from Field of Dreams. Wealthy magnate bankrolls wife’s brave struggle is a different trope altogether, especially when it happened in real life.

Nor can female “Cinderella” movies be gender-swapped. Just try to envision Pretty Man instead of Pretty Woman. You can’t argue that American Gigolo is the opposite-sex version, either. Richard Gere’s motivation in that one is clearly not to find an ideal wife (or to find a woman and make her into a perfect wife). It’s a gritty murder mystery with lots of sex, not a lighter-than-popcorn whore-makes-good success story. Richard Gere is the fantasy “prize” in Pretty Woman, not an accused murderer.

Note: This is not true of all rom-coms. You could make a case for Working Girl/Working Boy, in which the mailroom clod gets a makeover and lands a top job and the luscious female reward. In fact, it’s been done.

But do this exercise: Take any of your favorite movies and see if they could even remotely be envisioned gender-swapped. Lord of the Rings? Chicago? Beauty and the Beast? It tells you something about the movie.

Of course, there are plenty of movies that could be gender-swapped: It’s a Wonderful Life has been. Avatar, possibly could be. Beverly Hills Cop, hell yeah!

Not that I’m saying all these films should be gender-swapped. I’m just asking you to think, “What if they were?”