Viv Groskop: Did you know Miss Piggy is really a man?

No cartoon is complete now without some ball-breaking girl who proclaims her independence

I happily got exactly what I was expecting from the new Muppets movie. The ultimate in divadom from Miss Piggy, kamikaze stunts from Gonzo. And the most crazed drumming yet from the most muppetational of Muppets, Animal, who also had the best line of the film. Jack Black: "Animal, what are you doing?" Animal, wild-eyed and foaming at the mouth: "Acting. Natural."

I also got something I was not expecting. The revelation that feminism is alive and well in Hollywood. Sort of. Trailed ahead of the film and coming soon to a screen near you: Brave, the Disney Pixar story of a Viking princess, and Mirror Mirror, featuring Snow White turned Boudicca and Julia Roberts as a super-bitchy evil queen. Hey, I didn't say it was subtle feminism. Even The Muppets: The Movie was gender-aware. Amy Adams sent up the idiot romantic lead beautifully, just as she did in Enchanted. Miss Piggy appealed to the sisterhood. And the sharp-suited, ambitious TV executive trying to shut down the show was, of course, a woman.

Children's movies now make a point of reaching out to mothers. A smart move. Because we paid for the tickets. Including £7 for an empty seat for an 18-month-old who sat on my lap throughout. Do we buy the message, though? "Just because you're a girl, it doesn't mean you can't do whatever you want." Who would disagree with that? The trend started with Mulan in 1998, a story about the only daughter of a warrior. I haven't seen Brave yet but I'm guessing it is basically Mulan with ginger hair and Scottish accents. Billy Connolly's booming tones feature heavily.

Now, no cartoon is complete without some ball-breaking girl who proclaims her independence or intelligence: the Rapunzel character in Tangled, the geek reporter girl in Cloudy with a Chance of Meatballs, the Princess who really wants to own a restaurant in The Princess and the Frog. (Yes, that really is the plot. It is quite good.) At Toy Story 3, the audience cheered when Barbie got her revenge on Ken. I thought it was a bit unfair. He gave good outfit.

All this is to be applauded. But it also highlights a massive disconnect. You pays your money, you gets your feminism for 90 minutes. Then the credits roll and the fake world of feisty equality represented in these films collapses. All the main Muppets are voiced by the same seven men. Thirty-six star Muppets! No women! It's time to start the music and light the lights. But it is not time to let a woman voice Miss Piggy.

Mirror Mirror has a woman writer on the team but was directed by a man and exec-produced by a team of – count them – 13 men. Brave is hopeful: a woman co-director, a woman co-producer. More of this, please. In the meantime, thank you for the thought, film-makers. Maybe when you extend the effort to the names on your roll call, we can wake up from the fairy tale.

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