And they're all played by one actress: 28-year-old Tatiana Maslany.
As the star of BBC America's buzzy smash – which makes its season 2 debut on April 19 – the Canadian breathes life into a total of eight different clones – and often more than one in a single scene.
"It's definitely a technical challenge," she tells PEOPLE of acting against herself. "Eye lines and marks and rhythm become so crucial. If any one thing goes off, we have to do the take again because it's really about precision. It's a challenge, because at the same time I still want to be loose and responding in the moment. It's a fun conflict to play with."
There's another key challenge, as well: Maslany, who was nominated for a Golden Globe earlier this year and nabbed a Canadian Screen Award in March, pulls off a variety of distinct accents, from Sarah's London dialect ("the most challenging") to Alison's Midwestern cadences.
Does she have a favorite clone?
"It's different all the time, but I get to do some nice comedy stuff with Alison," says the star, who grew up in Saskatchewan and did improv comedy professionally for 10 years prior to breaking out on Black.
"Improv is completely invaluable when it comes to acting and character creation," she says.
Also providing a major assist is her clone double, actress Kathryn Alexandre, who frequently acts opposite her and is later replaced in the final cut.
"She does a lot of scenes with me, or at least her voice is there," says Maslany. "So I have an actor to work off of when it's not a tennis ball!"
Still, it's up to "Tat" – as her costar Jordan Gavaris affectionately calls her – to shoulder the bulk of the series, working up to 18 hours some days.
"It's pretty intensive," she says. "At the end of the day I just pass out."