It's the end of Sergeant Wu as we know him, and actor Reggie Lee feels pretty fine about it.

Reggie Lee as Sergeant Wu on Grimm

Reggie Lee with his "NeanderWu" stunt double on the set of Grimm

"It's interesting, because I didn't think I would ever be here," he said during a visit to the set of Grimm when the series was filming "Good to the Bone." "I always thought I was like the human that was safe -- safe being a relative term in Grimm."But no one is safe on Grimm, and now Wu has gone full "NeanderWu," as they called the non-Wesen Lycanthrope creature he transformed into in tonight's episode. Initially the creature was going to be Wesen in origin, but NBC told the Grimm writers that they couldn't change the rules with werewolves on the show.Even Lee didn't know if it was going to be a permanent transformation when "Good to the Bone" was in production. He studied up on werewolves and Neanderthals to try to get as deep into character as he could for his first woge on Grimm."This episode and the next episode are really pivotal, and that's why I asked for a lot of [prep time]. I'm crazy about my prep time, but when there's an emotional change and a physical change, I think it's integral that I get it as accurate as possible for myself emotionally," he said. "I always try to play this as a real human being going through these things."Lee added, "They call him NeanderWu, just FYI. It's in the script. Then I started reading up on Neanderthals. They're a completely separate species all together. They're thick and they're about 5'5". They walk like we do; they don't walk like apes, they're just primal. He is this very, very primal being. It's kind of a good juxtaposition to Wu, who's not."Originally, makeup FX designer Barnie Burman wanted to get Lee into costume for the NeanderWu transformation, but ultimately the decision was made to bring in a stunt double."I actually think the guy doubling him as NeanderWu has got the bulk, the muscle. It was so much fun to find a way to bring Reggie's face into him in the sculpture so there's some consistency, some continuity," explained Burman. "I've studied Reggie's face more than I ever cared to, more than I ever should. We took about three hours to do the makeup, but there was about six or eight days of prep back in my studio back in LA."David Giuntoli and Russell Hornsby were both also on set when Lee was filming his big transformation in February. Neither of their characters know yet what Wu is going through, but Giuntoli at least is excited for Nick to find out."I just want to walk in on him doing cave art, like painting onto his hand and leaving his imprint," he said. "Finding a love and then eating it. I think Nick is well suited to deal with these ramifications. If anyone were, I think Nick's the guy."Lee has heard that there should be some sort of big resolution for his story arc by the final two episodes of the season, but for now he hopes there's some deep, interesting impact for Wu's supernatural transformation."I really hope, as a police officer who has always abided by the law, that if this change occurs and it's a permanent change, that he uses it for good rather than evil, because I don't think Wu would do that. It wouldn't be congruent to his character at all. I think he'd want to help," Lee said. "I'm scared and excited to see where this goes."

Grimm airs Fridays at 9 p.m. ET/PT on NBC.Terri Schwartz is Entertainment Editor at IGN. Talk to her on Twitter at @Terri_Schwartz