@TheAntiCat  
Because to me she seems like a cosplayer. :P

@Ping_chan  
Yes, that’s very true. She could still have created her design by herself and for herself.
 
But please, keep beating your head into the wall with the idea of her cosplaying.

@TheAntiCat  
There’s a lot of made up pop culture in the pony/EG worlds, mostly to fill in “we need a adventure/super hero/comic book episode” without touching copy rights.  
It would be like if a pony who is a fan of Starswirl the Bearded/Daring Do/Mysterious Mare Do Well/what ever those heroes from Spikes comic books were, to meet a human from our world and compare their knowledge.  
Telling the pony about Indiana Jones and Gandalf the White would be kinda pointless.  
While Trixie is simply just a stage performer, it wouldn’t surprise me if her look with the hat and cape could reference something unique to their world.

@Ping_chan
 
@Lancalot  
Who would she be cosplaying anyway? Herself? She’s a magician. Magicians historically wear capes and hats.

@Ping_chan  
Okay, but she’s not. She has a hat and a cape. If you consider that cosplay, then if someone throws on a top hat they’re cosplaying.
 
Wearing fancy clothes =/= cosplay.

If the only clothes that Trixie owns is cosplay clothes, then she’s still wearing cosplay.

This is pretty much the definition of ignoring the elephant in the room. There is a girl with actual bird wings, horse ears, who sucks at dancing, and has a horrendous getup, yet the focus of this is Trixie. I find this quite funny.

Gets one-uped in the second movie three times…
 
LIKE A-…no not a boss…what’s the opposite of boss, Twilight?
 
Twilight: Like a bitch?
 
Yes, Yes, that’s it!
 
LIKE A BITCH!

“Some Blue Guy”, BAHAHAHA! How the hell have I not seen that character tag until now?

…She wore a cape and a hat? That’s.. not cosplay. Twilight is closer to cosplay than that.

It’s not Cosplay she’s a witch.

…You think that’s cosplay?

That’s not cosplay, that’s all the clothes she has.