Harvey Guillén Says Guillermo and Nandor Are "What We Do in the Shadows"'s Ross and Rachel

Harvey Guillén is flourishing, and so is his beloved character Guillermo on the FX series "What We Do in the Shadows." Guillermo is the human familiar to the vampire Nandor (Kayvan Novak), and in season one, he's a bit of a loser. He's been obsessed with vampires his entire life, and he's determined to have Nandor change him into one — but Nandor seems content to keep Guillermo as his low-level, disrespected familiar forever.

But in season four, which premiered on FX on July 12, Guillermo is in a totally different place. "He's just finding himself," Guillén tells POPSUGAR. "[Where] we started with him in season one is not where he's at now, obviously." He points out that in season one, Guillermo parted his hair down the middle and curled it to try to look like Dracula, thinking that was the aspirational vampire life he wanted.

"As time goes by, he finds out that he's actually more of a badass just being in his own self and his own body," he says. "I would say that he looks just more confident this season." Guillén purposefully sprinkled Guillermo's growth throughout the three previous seasons so fans could feel the transformation play out slowly.

But he's done such a subtle job that at moments in season four, it's almost jarring to see this more actualized, assertive Guillermo. Guillén says even his castmate Matt Berry, who plays the vampire Laszlo, was taken aback by Guillermo's new attitude toward the vampires. "Matt felt uncomfortable on set because of some of the lines that were given [to Guillermo]. Matt was like, 'Would he answer him like that?' And it's like, 'He does now,'" Guillén explains. "New Guillermo, who this?"

This season, Guillermo is still finding himself, but he's finally stopped putting the needs of the vampires ahead of his own. "He's going to totally just look after number one," he explains. "These vampires are not making him into a vampire anytime soon. So he's like, 'Well, what the f*ck am I worried about?'" And, of course, Guillermo has the ultimate trump card — he's a Van Helsing, and his vampire-killing powers have only grown over time.

The other big change moment for Guillermo happened off screen between seasons three and four, when he and Nadja (Natasia Demetriou) lived in London for a year before returning to their Staten Island coven. "He's seen the world, he's gone to London for a year. He's lived abroad. He's like, 'It is so much bigger than Staten Island,'" Guillén explains. "It's gotten to the point where he's just not caring anymore."

In episode four, which premiered July 26, Guillermo's new skills are fully on display when he and Nandor face off in a fake battle for a vampire crowd at the Night Market. Guillermo's combat skills are much better than his master's. "Now he's good with swords. . . . The backstory is that he's probably trained in London while he was there," Guillén says of Guillermo's talents. "While Nadja was at the council, he was picking up lessons and getting better at his craft and really leaning into his Van Helsing side."

Guillén says the Night Market episode is one of his top two favourite instalments from season four, and it's all thanks to his big fight scene. He compares learning stunts to working on a stage musical: it's all about timing. "You learn the steps, do the feet, and you have to be funny. And you have to do your lines on top of the sword fighting. And you have to do movement, because if you move on the wrong foot, you'll hurt someone," he explains.

The other thing Guillermo picked up on between seasons three and four? A love interest, whose identity hasn't yet been revealed in the first few episodes. Guillén promises we'll learn just who this person is soon, but for now, it's made Guillermo's relationship with Nandor, which always sizzled with an undercurrent of something, much more complicated. Guillén compares Guillermo and Nandor to a post-breakup Ross and Rachel on "Friends": trying to stay collegial and not to pry into the other person's dating life, but still a little obsessed. Guillermo has this new person, and Nandor has brought one of his wives back from the dead, but are they really over each other?

"I don't know," Guillén says. "The thing is that they have love for each other. . . . People can love someone and not necessarily be married to them. People can love someone and not be in a relationship with them. There's different kinds of love. And they definitely have a connection, and their love is so strong that people are rooting for them."

Guillén understands why some fans are desperate for them to get together, but he won't reveal if it'll ultimately happen. "Anything's possible, because they're still growing and learning," he says. "And so this year, they're going on these journeys, some together and some on their own. But also they're going through self-realisation, and sometimes you need to work on yourself."

The actor is excited for fans to see where Guillermo goes this season, saying his journey has been "a long time coming." He promises viewers will get to see more of his family and the dynamic of the Mexican household where he grew up. But Guillermo is still growing. "[People will] see a side of Guillermo that he himself has not been completely honest with," he says. "He's going to be asking a lot of questions." The answers will come in time.

"What We Do in the Shadows" airs Tuesdays on FX and the next day on Hulu.