The actor spilled on the vampire comedy's upcoming season, which recently wrapped filming in Toronto.
While What We Do in the Shadows has only recently finished filming season 5, that's not stopping star Harvey Guillén from spilling some details about what's to come for his character, Guillermo de la Cruz, in the upcoming episodes.
"We just wrapped last week," the actor tells ET's Rachel Smith while promoting his voice role as Perrito Perro in the upcoming animated film Puss in Boots: The Last Wish. "It's my first interview after wrapping."
And when it comes to Guillermo's arc, especially after the character became disillusioned with life as Nandor's (Kayvan Novak) familiar and decided to take the money he embezzled from Nadja (Natasia Demetriou) to pay a friend to turn him into a vampire in season 4, the actor teases that there's an emotional rollercoaster in store.
"It just keeps getting better and better. And I don't know how the writers do it," Guillén says of being continuously fulfilled by the way each season continues to progress with "the trajectory of his character."
Looking back on the first four seasons, the actor recalls how Guillermo went from being a servant who always wanted to be a vampire before finding out he's a descendant of Abraham Van Helsing. He eventually uses those newfound fighting skills to become a bodyguard for the rest of the household. And when it comes to taking money from the nightclub, it's "not because he's stealing but because it's rightfully his," he says.
"I've been like, 'Wow.' Every year just keeps getting better and better," he continues, before adding, "I will say, this year, for a comedy, I feel like Guillermo has gone through a rollercoaster and I've never cried as much."
"That's all you get," Guillén quips, without getting more specific.
And without revealing who he's set to play in the upcoming DC Universe film Blue Beetle, which he finished filming earlier this year, the actor did drop some hints about his role. "They haven't announced my character yet, but I will tell you this: they are crucial in the universe of Blue Beetle and just in the whole making of it," he says. "That's as much as I can probably share."
Until What We Do in the Shadows returns to FX and Blue Beetle hits theaters next year, fans can catch the actor in the final installment in the Puss in Boots animated franchise, which opens in theaters on Dec. 21. He joins Antonio Banderas, who returns as the titular feline hero, and Salma Hayek, who is also back as Puss' love interest, Kitty Softpaws.
When it comes to the scrappy little dog Guillén voices, he describes him "as a glass half full, optimistic, full of heart." He adds, "I think we all need and deserve a Perrito in our lives. As a friend, your biggest supporter and your cheerleader."