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Cadet Sylvia Tilly, the youngest member of the USS Discovery’s crew, is wide-eyed, brainy, chatty, and intensely chipper. When the character (played by Mary Wiseman) first showed up in episode three, she made me cringe. But over the course of the season, she has completely won me over.


Discovery’s first two episodes chart the deadly mistakes made by main character Michael Burnham. By episode three, Burnham’s a disgraced, depressed mess, dead-set on spending the rest of her unhappy days feeling guilty about starting a war, watching her beloved mentor die, etc. She’s absolutely not in the market for a new BFF, and that goes double once she meets the bubbly Tilly—who couldn’t be more thrilled to have a roommate, something she’d previously been denied due to what she calls her “special needs.”


Does that mean that Tilly is on the autism spectrum, as some have speculated, or does it just mean she’s just more geeky (and allergy-prone, which makes her snore, as Discovery delights in reminding us) than what we’re used to seeing in Starfleet’s ranks? It’s never clarified. All we know is she doesn’t read the room very well and comes on way too strong. As far as uncomfortable conversations go, it’s hard to beat this one:

Tilly: “What’s your name?” Burnham: “Michael.” Tilly: “I never met a female named Michael before. Do you think that suits you? I’ll call you Mickey, I think that’s a little more approachable!” Burnham: “No. You. Won’t.” Tilly: “[mutters] Oh yeah, no I won’t. [normal voice] The only other female Michael I ever heard of was Michael Burnham, the mutineer. You aren’t her, are you? [long pause, nervous laugh] Are you?” Burnham: [silent glower]

Next time they meet, Tilly is so freaked out by Burnham’s bad reputation that she pulls a “you can’t sit here” in the engineering lab. Later, because she is a genuinely nice person, she apologizes—and by the end of the episode, after completing a dangerous mission together, they have a meeting of the minds over Alice in Wonderland.

While Tilly’s upbeat attitude may be a little grating at first, her gleeful embrace of Starfleet, science, and exploration soon feels like a welcome and necessary counterpart to Burnham’s grimness. Before long, Tilly (who says daffy things like “I love feeling feelings!” and somehow makes them feel sincere) and Burnham forge an actual friendship—they go jogging together in matching “DISCO” t-shirts, in a scene in which Burnham actually cracks a smile. Tilly even encourages Burnham to act on her attraction to Ash Tyler in the time-loop episode. Remember way back in episode seven, before two major characters were revealed to be made of pure evil, and Discovery had a freakin’ party? And Tilly was the beer-ponging life of that party?


Ah, simpler times. But amid Discovery’s many insane and often frustrating dramatic twists, this friendship in particular helps keep things more emotionally grounded. Tilly’s sole purpose isn’t to make Burnham—who can be a challenging character to root for—more of a likable person, but it’s definitely one of the reasons she’s written the way she is, and the show is better for it.


As the series has progressed, and the action has ramped up far beyond the decks of the Discovery, there’s been less time for bonding over breakfast burritos. But that doesn’t mean we’ve seen any less of Tilly; maybe more than any other supporting character, she’s had a solid arc that’s seen her mature from nervous nerd to Stamets’ indispensable, quick-thinking right hand. (That right there is proof that Tilly’s talent for dealing with prickly people didn’t stop with Burnham.)

So yeah. She manages to buddy up with Burnham, the most mistrusted and misunderstood woman in the galaxy. As she herself says, she’s the best theoretical engineer around, and she becomes a major asset when things segue into crisis mode. And, yes, she’s the first character on Star Trek to say the word “fuck” when she exclaims, “This is so fucking cool!” after a breakthrough while working on the spore drive. She’s also the first person to reach out to Tyler when he’s made totally human again, and she encourages Burnham to make her peace with him, too. But the moment I knew Tilly was my favorite Discovery character was when we all learned about her Mirror Universe counterpart in the fearsome Terran Empire. Of all the twists this show has pulled, this is one I truly loved.


Yep, that’s Captain Sylvia Tilly to you, lording over the Mirror Universe version of the Discovery. “Uh... that’s me,” Prime Tilly stammers. She spoke in her very first episode about wanting to make Captain one day, but not like this. “You gained the rank of Captain by stabbing your previous superior in bed,” Burnham informs her. We also learn her nicknames include “the Slayer of Sorna Prime,” “the Witch of Wurna Minor,” and “Captain Killy.” Also, instead of Prime Tilly’s wild, wonderful red hair, Captain Tilly has sleek blonde locks. “Well, my mother would definitely approve,” she mutters, calling back to an earlier episode where she mentions her mother loved to criticize her hair.


In the scene where she’s trying to get into character as her Mirror counterpart, who else but Burnham is there to help her pretend to be “a twisted version of everything I’ve ever aspired to be.” And what a pep talk: “You have the strength of an entire crew that believes in you. Fortify yourself with our faith in you.” Of course, Tilly nails it: “If you greeted me that way, I’d cut out your tongue and use it to lick my boots,” she spits at a Terran who needs an attitude adjustment.


Meanwhile, all that Barbie hair doesn’t prevent her from making ingenious progress on bringing Stamets back from the spore-drive void, impressing yet another prickly personality: First Officer Saru. And then (with her natural coif restored), she excitedly helps a revived Stamets figure out how to guide the Discovery back into its proper universe. On a show that’s felt awfully full of secret Klingons, double-crossers, torturers, snooty aliens, and catty scientists, Tilly is a ray of sunshine beaming straight from the heart of everything good that Starfleet stands for—and she’s super fun at parties, too.