From this tumblr prompt:
elviswithoutthetassels:AU in which Maura & Jane head to the BPD Halloween Party dressed as Emma Swan and the Evil Queen from Once Upon A Time…..

I wrote a Rizzoli & Isles minific (which you can find here; it's titled 'Once Upon a Cosplay') , and one of the responses was:

tinyregaltimelord: This should totally be made into a full blown story because this is amazing! Or Regina and Emma going as Jane and Maura to a Halloween party

Well, how could I resist? I don't have plans to expand this, but I enjoyed it enough I wanted to post it here.

Characters aren't mine. They belong to ABC, Disney, and other assorted entities of importance. I gain nothing from writing these stories but the fun of doing it. Please don't sue me.

"Stop pouting, Regina. It's not even that much of a costume. I mean, you wear pants suits all the time." Emma rolled her eyes and doubled checked herself in the full length mirror of the master bathroom. She smiled at the way the designer dress hugged her curves and the high class high heels made her legs look amazing. She didn't often dress 'like a girl', but, when she did, she was always pleased with how well she cleaned up. Glancing at the brunette as she pulled on the Boston Coroner's office lab coat, she narrowed her eyes. "Is that my gun you're wearing?"

"No, of course not. You know how I feel about guns." Regina ran a hand over the top of the gun's handle, her finger running across the top of the replica Boston Homicide PD badge that sat next to it. "I don't understand why my hair has to be so unruly. Doesn't this Detective Rizzoli understand what a comb is used for?"

"I kind of like you with longer hair." Emma shrugged, walking over to the other woman to double check her costume. "Besides, Rizzoli's a no nonsense cop who doesn't care about how she looks."

"That would explain the terrible fit of this pants suit," Regina muttered.

"Come on, Regina! You could at least pretend to be enjoying this. You and I have been watching that show for months now, and I know you like it."

"Enjoying a show and dressing like characters from the show are two different things, Emma," the brunette growled. She held her had up to stop the next thing out of the sheriff. "I know you're about to tell me it's Halloween and we agreed to go in costume to Henry's school's party, but I feel I've already made it clear that I've reserved the right to protest."

"You mean complain," Emma corrected with a smirk on her face. "Besides, I know you like this. I can tell. You have more of a swagger in your walk. You know what I think?"

"Please," Regina replied dryly, "do tell."

"I think you like the way it feels to wear a gun and badge on your hip." Emma's eyes sparkled. "You know what else I think?"

"It's funny you should ask," Regina replied with a roll of her eyes, "because I sodo."

The blonde chuckled. "I think it all looks good on you, sexy even, and, after we get Henry to bed tonight, Detective, I plan to show you exactly how sexy I think it is."

Regina smirked, mimicking the detective she was so accurately dressed as. "Well, Doctor Isles, since you put it that way," she offered her arm, waiting until Emma took it, "shall we go?"