The following article is purely my opinion, based on how I felt watching the episode, it may differ from your own opinions. What I am presenting here are my own thoughts only, and as such it should be viewed not as 100% universal, but just one view amongst many.
One of the new episodes of The Powerpuff Girls features a 'transgender' unicorn character called Donny, who is a horse that believes he is a unicorn and has the girls help him attain his goal. Whilst the show is trying to send a message about transgender people, I found that it went and did the opposite.
The series executive producer Nick Jennings spoke about the episode and said, 'Basically when we start out, he's a pony, but he wants to be a unicorn. He has to go through a transformation to become a unicorn so it's a whole, 'What are you on the inside? What are you on the outside? How do you identify yourself? How do people see you?' There's a lot of subtext to that.'
'I don't think you can be too young to start talking about those issues and those things and just presenting an attitude, a voice that is going to resonate with people.'
For first main issue is this, why go through the whole scenario of a horse who believes he's a unicorn? I get that it's a metaphor, but why not just have a trans character instead? Clearly the creators don't think that their audience are too young to be learning about and thinking about gender, so just talk about it rather than using a metaphor. Trans people exist, we're not metaphors.
I found the actual content of the episode itself to be contradictory to the idea of expressing a pro-trans message that the creators say they were trying to convey. When we first see Donny he's wearing a horn to be a unicorn and Buttercup immediately rips off the horn, says he's not a real unicorn and reduces him to tears.
So, essentially what we have here is one of the heroes confronting our trans character and saying that they are fake, that despite trying to make himself look like a unicorn he's not. To me, seeing her rip off his horn and call him out is no different than seeing someone pulling off a trans woman's wig and calling her a man.
Does this mean that Buttercup is taking the place of a transphobe or someone that abuses trans people? It certainly looks that way, and she's the hero! What kind of message is that telling children about accepting someone's gender identity?
When Bubbles tries to get the Professor to help Donnie there's a whole big scene about the multiple dangerous side effects of undergoing such a transformation, at which point Donnie ignores all of these dangers and immediately signs under a big red 'Forever'.
When I saw this part of the episode it looked like the writers were trying to say that trans people are so desperate to sign up for medical procedures that 'last forever' that we ignore dangers to do it. Whilst there can be some dangers in medical transition it's wrong and misleading to portray it like this. There's no real greater danger in changing gender than there is in many other medical procedures, don't go and make out that trans people rush into unsafe medical procedures because that's just plain not true.
When Donnie goes through with his transformation things go wrong and he transforms into a monster, a literal monster and goes on a rampage. What exactly is the message here, that if you try to change your body you will become a monster? Are they trying to say that trans people are somehow monsters?
Add into this the fact that characters, including members of the Powerpuff Girls themselves, call Donnie a freak more than once at this point and I can't see it as anything positive. The message they're conveying is, if you change your body to try and match who you are inside you will be seen as a 'freak' and a monster.
Add onto this the fact that at the end of the episode it turns out Donnie was a unicorn all along and gets changed back into his true self, what's the point of this episode. Donnie isn't a horse who wants to be a unicorn, he's already a unicorn. The message at the end is 'be who you were born as'.
The episode might have been made to comment on gender, but I really don't think it was trying to make a good point. Donnie is mocked for trying to be who he feels he is, he signs up for dangerous medical procedures without a car, he becomes a monster and gets called a freak, and the end message is 'don't try to change yourself'.
Like I said at the start, this is only my personal opinion, but I do not see this as a positive message about trans people hidden behind a metaphor, I think it's an incredibly negative message about trans people. I'm extremely disappointed in this episode, but it just seems to add to a history of the show mocking trans characters and queer coding villains.