HBO describes the character as "young, outspoken, smart, career-focused, but exhausted by responsibility." McEvoy "loves building and fixing things" but is "terrified of dying in space."
She doesn't seem overly fond of babies as seen by her awkward reaction in the delivery room during Was It Your Ears? and by the fact she stands firmly away from both mother and child while Clark happily holds the newborn, later named Kayden.
Billie is a woman of approximately thirty-five - probably part of Generation Alpha - with a slender build and mocha skin. She's got brown eyes and brown hair which is styled in an afro. Billie can often be seen in an engineers jumpsuit of either green or red; the green of which has a large 'J' on the back which, of course, stands for Judd.
Billie is the Second Engineer aboard the Avenue 5. She originally reported directly to Joe but after his death was forced to take over his workload on top of her own, as well as anything else that came along to damage the ship. She only really has the small team of engineers from the Real Crew for aid and is often left doing most things alone. Though essentially forced into the role of Chief Engineer she hasn't been formally given the job and has never sought recognition as such despite desiring acknowledgement for her hard work; the closest she's ever come to commendation, or so much as a pat on the back, is from her interactions with Ryan Clark and even he can be dismissive occasionally.
After the death of the First Engineer due to the gravity shift, Billie is left to pick up the slack. She quickly ends up relying on Clark to help her with getting the facts across to Herman Judd and the pair are left trying to keep things running. She is the one to go outside the ship and bring Joe's body back then later has Cyrus perform calculations to work out exactly how much extra time the gravity shift incident had caused.
In I'm a Hand Model she is finally forced to reveal to Clark that there is a small team of engineers stationed below the bridge keeping things maintained while the Bridge Crew he's been working with are all actors. She then introduces Ryan to everyone below expecting them to abhorrently hate him, yet is quite pleasantly surprised when they all quickly take to him for his sense of humor and how down to earth he is.
When the wetsuit ruptures during Judd's live stream because the Real Crew forgot to vent it she is the first to notice and jump into action. Irritated that everyone pushes Clark to go out and deal with a problem he knows nothing about she gives him a communication device and says she'll talk him through everything. Billie remains on the bridge to try and keep up the act only for Spike Martin to butt in. This actually works in her favor as it gives her an opportunity to suit up and go outside to help Clark with the valve. Together they manage to shut off the sewage gushing from the ship and head inside.
Throughout He's Only There To Stop His Skeleton Falling Over Billie is excited and happy about their hard work being seen on the live stream believing people all over Earth to have seen her saving the ship. Despite this is slowly becomes obvious to Billie that people have only taken notice of Captain Clark and are showering him with praise while she gets little to no acknowledgement at all, this slowly wears on Billie and leaves her slightly resentful of Ryan though this soon fades when the Half Way Home party descends into a bar brawl.
After the birth of the first baby in space she and Clark notice an odd beep that they cannot find the cause of despite roaming the entire ship looking for it. Eventually Spike Martin comes to them and suggests the beep could be an alert that there is an oxygen leak. This causes concern for them as well as Iris and Karen who are informed a few moments later and they discuss if they could make it back to Earth or not. Since Billie hadn't found any other issue that could cause the beep Spike's theory is grasped on to as the most likely culprit.
Along with Clark, Iris, Matt, Karen, Judd and Mia she attends a meeting for the passengers and crew to discuss any issues they may have with one another. When Clark spills his coffee she and Karen have to dispel Mia's suspicions that Ryan is actually British by claiming the accent change as a joke. She is tired and overworked by the time the meeting starts and doesn't appear all that concerned with anything as seen by her openly confirming they only have nine months of air left. She quietly listens to Judd's plan to turn the faecal matter orbiting them into a positive thing. They then talk about conserving oxygen most notably by not letting fat people use stairs. After the meeting she, Clark, Karen and Iris all talk about sedating Judd and Billie points out that Matt monitors the supply and that he'd probably have access to drugs. The group then speak to Rav Mulcair who is back at Mission Control and learn they have been granted emergency aid funding by both presidents. Unfortunately the connection breaks down due to Jupiter before they finish their conversation and the group is left wondering if Rav intends to have the five-hundred non-essential personnel killed.
Eventually Billie figures out that the beeping is actually the ship telling them to recalibrate for the new baby on board and not an oxygen leak which releasers everyone's stress. Thanks to Doug and Mia knowing about the possible killing of people though a shouting match instantly starts up in Karen's new office until Judd's stupid idea to blast glitter and lights into the ring of excrement actually turns out not to be stupid and instead is rather beautiful.
She comes up with a plan to jettison items out the back of the ship in Are You a Spider, Matt? in order to push them forwards so the ship could meet with the rescue ships within six months. Shortly after Clark announces the plan to the passengers they realize it's not a good plan as the six months wouldn't be nearly enough time for Clark to learn how to dock the ship.
As suspected Clark struggles to learn how to dock the Avenue 5 and continually blows the ship up on the simulator that Billie uses to teach him in This Is Physically Hurting Me. While trying to keep everything working she passes Karen Kelly who doesn't help Billie's workload. Billie tells Karen to just move the golden statues and use them as her donation before she scurries off back to work. She eventually stumbles across Clark looking like he's been robbed and is informed that he had quit as captain - though Judd insists he's been fired - and instantly starts to panic as the passengers start to think they're in a reality show and that they could simply walk out the airlock because they weren't really in space. Sarah makes this worse by basically telling everyone that the Bridge Crew are all actors. She does her best to stop people jumping out the airlock but even between herself, Clark and Matt Spencer one passenger - Mike - still jettisons himself and dies instantly. This splits people in two, those who have come to their senses and those who believe it all to be computer generated. After Harrison Aimes offers money to those who help him get off the ship the airlock opens again killing Aimes and another female passenger, Billie is also nearly sucked in with them but Clark grabs her and pulls her to safety. After the final set of deaths the passengers finally accept it's not fake and give up on the idea.
After the deaths and Matt absconding with the new airlock codes Ryan orders that she and the others break down into small groups to search the ship. Billie ends up being sent with Jordan Hatwal and Nadia, which she seems pleased about probably due to her recent relationship with Jordan. While Nadia cries over Sarah's death in the elevator she receives a communication from Cyrus informing her that they'd need to go outside the ship and cut off Joe's hands so they could use him for print recognition in case Clark couldn't dock the ship. Due to Ryan's mini breakdown and the fact he'd never docked the ship in the simulator without crashing she agrees to Cyrus' plan.
Eventually she, Jordan and Nadia stop actively searching for Matt and break for a drink and chat. She learns that Jordan should have been on Earth to star in a new show called 'The Smasher' and while she tries to be supportive of it, the idea of the show clearly doesn't interest her at all. As Nadia slowly grows more and more depressed she gets Jordan to try telling her a joke which actually works out rather well and makes her laugh.
When a free for all breaks out over the vacant shuttle seat which Jordan had started in an unsuccessful attempt to escape the ship, she refers to him as an 'unclear joke' and turns her attention to Cyrus when he enters with pieces of Joe in a clear bag. The seat changing continues and Karen finally has everything jettisoned out the ship but she uses the port airlock rather than the rear forcing them to be trapped a total of eight years.
Due to necessity Billie and Ryan Clark form a quick friendship in which they come off almost as co-conspirators. The pair often discus things between themselves before raising ideas, theories or problems with anyone else - including the Real Crew - and will quickly come to one another's aid.
In He's Only There To Stop His Skeleton Falling Over Frank Kelly and his wife,Karen Kelly, are seen discussing and debating if Billie and Ryan are a couple. While Frank thinks they are, a theory which is probably brought on by his own insecurities, Karen believes Clark would prefer a more mature woman. Later in the episode when everything goes wrong at the Half Way Home party Billie and Clark decide to remain a team and 'stick together'.
As soon as Billie announces that there isn't an air leak in Was It Your Ears? Ryan goes over to a bench in Karen's new office and simply passes out. Without prompt Billie takes some blankets and covers him in one while she folds the other up as a pillow that she gently slides under his head.
While Billie is on her date during Are You a Spider, Matt? Clark notices almost instantly that she's with Jordan Hatwal while no one else so much as glances in her direction even when she laughs in that strange way of hers.
When Spike Martin and Matt Spencer take a wrong turn looking for Tabasco into the Real Crew's headquarters Matt makes a comment right before they leave again suggesting that Billie and Ryan have a 'role play thing' going on. Neither Ryan nor Billie say anything about it and ignore the comment. Later when Aimes goes to his death out the airlock Billie is almost dragged in with them but Clark grabs her tightly and pulls her away saving her life.
While Cyrus and Billie aren't exactly friends they certainly aren't enemies. They work together aboard the ship to keep systems running and perform maintenance along with the rest of the engineers and have a sort of working respect for one another; though they'd be unlikely to admit to it. They constantly butt heads which probably started around the same time Billie beat him for the NASA internship many years previous.
Billie paid Jordan Hatwal very little attention for the first part of their journey. She eventually runs into him while cutting through the bar to Engineering where he recognizes that she saved the ship from the wetsuit and asks to test some new jokes on her, she doesn't understand them and quickly excuses herself. Despite her original disinterest Billie does return to the bar later for a date where the pair talk further about his comedy, Billie gets distracted by Clark's outburst at the Captain's Table though and ends up running off with an idea.
In Eight Arms But No Hands Jordan cons Judd out of the shuttle in an attempt to get himself home which fails, as a result Billie looses all respect and interest in him essentially ending whatever relationship they could have had.
- "Space is cold, Captain. You know that right? Joe's blood is frozen." (Billie to Clark)
- "He says he's had four long term relationships, and that his band has been downloaded 90 million times." (About Cyrus)
- "So, uh, there may be some more bad news, or as I'm learning to call it, news." (Billie to Clark)
- "The three injured passengers, no longer injured ... they're dead." (Billie to Clark)
- "Well, um, my concern is that, uh, you have no skills as a captain beyond fuzzy charm which is already kind of getting old. You can't seem to hold the same accent, which is kinda crazy. And, uh, also, if you hand me the mic again to talk to those passengers, I will beat you over the head with it and I will ram it down your esophagus." (Billie to Clark)
- "You! You need to handle Judd the business Sasquatch, 'cause otherwise he starts flinging his shit and telling NASA to go fuck themselves." (Billie to Iris)
- "So, if trajectory porn is your thing, prepare to get your rocks off." (Billie to Clark)
- "You know - and this has never happened before - I don't actually know." (Billie to Clark)
- "These people are so dumb, I'm just hanging out with pigs and dolphins when we get back." (Billie to Clark)
- Billie usually doesn't drink because it makes her 'blunt and opinionated'.
- She doesn't understand a lot of comedy.
- Billie has a very peculiar laugh similar to somewhere between being half hyperventilation and half about to cry. It's also rather loud. Only Clark seems to like its over the top nature.
- HBO. Armando Iannucci to Bring Humor to Space with ‘Avenue 5’ hbo.com. Retrieved on November 24, 2019.