On Saturday Night Live and in countless comedy sketches, a man dressed in feminine clothing is automatically the joke — the audience laughs the moment he walks out in a dress or heels, before he's even said anything. I started noticing how often my kids laughed at this without knowing why.
In almost every superhero movie aimed at kids, female characters who are 'too girly' are either comic relief or need to be saved. Meanwhile, female characters who are taken seriously are always coded as masculine — short hair, dark clothes, 'tough' personalities. My daughter noticed this herself and said 'girls have to act like boys to be important.'