Kids' films and the forces of counterrevolution

The following contains spoilers for old children's films. Not to be read by four year olds. 

Now I have children I think more about children's films. You know, they're harsher than you'd expect. 

Many have an element of something magical and wonderful coming in and making a child's life great. Hooray! However, this greatness is rarely allowed to last. Usually the wonderful thing will leave, and the child is returned to a regular life, with nothing but memories. Booo! 

Generally the wonderful thing -- a monster, alien, animal or magic thing -- is a Manic Pixie Dream Girl, a device to teach the protagonist (or, often, the parents of the protagonist) something about living life. (Loosen up, Dad, stop taking work so seriously.) 

Harry: Manic Pixie Dream Girl

However, unlike in films for grown-ups, the protagonist is not allowed to stay with the life-enhancing sprite. 

The plot of a mainstream romantic comedy is, and watch the self-conscious way I phrase the following so as not so sound sexist: girl and boy meet, girl and boy have a lot of fun, girl and boy have troubles, usually a misunderstanding, and are torn asunder, girl and boy get back together. The end. Everyone's happy. 

Compare with E.T. Boy meets Alien, boy and Alien have a lot of fun, boy loses alien, boy gets alien back. The End? No! Not the end. Boy loses alien again. THE END. Tears all round. 

E.T. is not a mismatched couple making good. E.T. himself is not a manic pixie dream girl (or "magical negro") as he has his own motivations and goals, and from them, internal conflicts. This is not romantic comedy but romantic tragedy. This is Brief Encounter, not Maid in Manhattan. 

Now, what's so bad about a happy ending? Is this simply that it is narratively expedient to put the world back the way you found it? Do more permanent changes in the imaginary world get in the way of suspending disbelief? 

Or this instead a deep conservatism? You can have your fun but ultimately you have to give up on the strange and fantastic and fit back into a world whose social relations remain intact. You have your memories, now work hard at school, get a proper job, get married, have children, vote: these are the messages of Batteries Not Included and Flight of the Navigator.

The kids never end up with the girl. We must wave farewell to Mary Poppins. She's done her job teaching parents to pay a bit more attention to the kids, and these are apparently all the lessons they need. Her goal is not permanent revolution, it is not breaking down the structures of bourgeois society and the family. Her actions underpin conventional living, as the welfare state underpins capitalism. Think what chaos she could cause if she stuck around! But no, she needs to go and make another upper middle class family that bit happier. Her magic is not for slum kids. 

Capitalist foot soldier

UPDATE! Just thought this might be why Roald Dahl so popular with children and still frowned on by adults. In his stories the world and its social relations are permanently changed. Nasty parental figures don't learn, they are killed! Children ascend to power, and not fairy tale power, which is often about reclaiming a 'natural' place in the hierarchy (lost princesses coming home etc), but new power.