Heads up - if you're a fat woman who wants to dress up as a popular fat character for Halloween, good luck trying to find a plus-size Ursula (from "The Little Mermaid") costume.
Disney DOES partner with a company called Disguise Costumes to offer those ubiquitous, often inappropriate "sexy" versions of characters, and they do offer an Ursula costume - but Ursula can't be fat and sexy at the same time, so if you're an actual plus-size woman, better look elsewhere. The "Sassy Ursula" offered in their "Fabulous Flirts" collection comes in sizes S, M & L - with L equal to a US 12-14. (The company does have a small range of actual plus size "Disney Princess" costumes - you can be Fat Cinderella or Fat Belle if you want to, but you can't be Ursula. Better luck next time, fatties.)
It's outrageously exclusionary - it basically tells fat women that we're too fat to play a fat character; it also tells fat women that in order to be sexy, a character must be made skinny.