Jodie Whittaker's costume as the Thirteenth Doctor in the upcoming season of Doctor Who may have alien influence, but it's also genderless. In fact, those genderless qualities apply to the Thirteenth Doctor as a whole as well.
Doctor Who is a 55-year-running science fiction television series from the UK that centers around the titular Doctor, a time-traveling humanoid alien who pilots a time machine called the TARDIS (which stands for "Time and Relative Dimension in Space"). Apart from occasionally scooping up companions on their travels and repeatedly saving the universe from various extraterrestrial threats, the Doctor has the unique ability to regenerate, wherein their body will physically take on a new form so as to stay alive (often getting a slight personality update in the process as well). And even though the Doctor has remained in a male form for the past 55 years, the regeneration process is hardly gender-specific. In the upcoming season of Doctor Who, the Doctor will have already regenerated into a woman, and Jodie Whittaker isn't convinced that gender is nearly as important to Time Lords as it is to humans.
During an official Doctor Who press conference at San Diego Comic-Con 2018, Whittaker opened up about her interpretation of the Doctor, revealing that gender takes a backseat to other fundamental aspects of the character - even her costume. She explained that when she approached the role of the Doctor, she didn't let the Doctor's shifting gender dictate her performance, saying, "I have never approached a role thinking of it as how would a woman play this role, because I just am one," adding that her approach to the character "feels genderless." And adhering to the concept that the Doctor rarely follows protocol, she elaborated on her response, saying, "It’s never been necessarily great to have a specific way a woman behaves and a specific way a man acts, but the best thing about the Doctor is I’m not playing either. I’m an alien, so there are really no rules."
Whittaker also discussed the inspiration behind her outfit, and how the Doctor's genderless qualities carry over to the way she dresses. Former Doctors Matt Smith and Peter Capaldi both played an active role in dressing their respective iterations of the character, and it was no different with Whittaker. After landing the role, she explained that she would send Doctor Who's new showrunner Chris Chibnall photos for inspiration, and the process ended up helping immensely. One of the photos she sent featured a woman whose clothes, hair, and overall attitude helped inspire the Thirteenth Doctor's look. Whittaker explained that "it was just a wonderful expression in one image of timelessness, purpose, and inclusiveness, all in one simple look," and that "it didn’t feel you needed to be a certain shape or age to wear it, or gender."
For the past 55 years, the Doctor's costume has implemented a vast scope of stylistic influences - from the stately ensembles belonging to the First and Eighth Doctors to the bolder, adventure-type getups on the Fourth and Tenth Doctors - and this Time Lord is far too concerned with self-expression to let something like gender get in the way. Whittaker just went one step further by officially speaking out on the character's unbounded identity.