Adventure Time is an unconventional children's show in a lot of ways. It's a kids show that's not explicitly made for kids, it's a cartoon about a human boy having adventures that features multiple strong, smart female characters, it's a show that did an entire noir episode around an adorable talking video game system. That's why it's especially strange for McDonald's to not only subject the Adventure Time toys for their Happy Meals to their backwards, gender-binary thinking, but also to not represent a single female character from the series.
This is a show that had two gender-swapped episodes, for Christ's sake! But not only are the show's toys firmly placed in the "boy" to category, they also only include male (or gender neutral) characters: Finn the Human, Jake the Dog, the Ice King, and the video game BMO (who may identify as both male and female).
There's a lot of reasons why the action figures from Adventure Time should not be inherently labeled "boy" and the pink heart-and-flowers Paul Frank toys should not be inherently labeled "girl." Gender expression doesn't work the same way for everyone, and kids shouldn't be made to feel like they're "weird" or going against the norm when they want a Finn action figure instead of a heart-shaped notepad with a monkey on it.
And, if you couldn't already tell, Adventure Time is far from a show that's "just for boys." There's an entire Candy Kingdom with adorable talking candy people! There are an infinite amount of princesses on this show! One of them is even entirely pink!
Even with the weird separation of the genders that McDonald's enforces with its Happy Meal toys, there's an obvious solution to this. Why not offer the boy Adventure Time toy's female counterparts for girls? The current girl's toys are passive and chiefly decorative: there's stickers, a notebook, a standalone figure, and a couple bracelets. In contrast, the boy's action figures are much more adventurous — they bend, they spring, they sword fight, they change colors. The division here is pretty clear — the boys go off and have imaginary sword fighting adventures while the girls... put stickers on things.
Girls need more toys and more role models like the female characters on Adventure Time. Those girls are just as fierce and adventurous as the show's heroes, Finn and Jake: they conduct experiments, they play guitar, they destroy things, they rule kingdoms, they play pranks. Sure, they're strong and smart (sometimes even stronger and smarter than Finn and Jake), but they're also flawed, they make mistakes and they represent different sides of femininity without sacrificing their integrity.
Princess Bubblegum may be an eternally pink princess who loves ballet, but she's also a confident ruler and the best scientist in the Land of Ooo. Conversely, Marceline the Vampire Queen is a sullen bass player who'd never be caught dead in pink, but the show points out that that doesn't make her a better or worse person than Princess Bubblegum.
Not only is McDonald's continuing to draw a line of separation where none exists, it's failing to offer up images of equally powerful role models for girls as it does for boys. And as Lemongrab would so eloquently put it, that is UNACCEPTABLE!