On NBC's "Grimm," they've found that X marks the spot — literally and figuratively — as the show airs its 100th episode Friday night with the discovery of a treasure first hinted at in the opening episodes five seasons ago. Though the once-important episodic TV milestone may have lost a bit of its significance, it's still a testament to the show's longevity in a world of Netflix, Hulu, Amazon Prime and YouTube.

The exclusive clip below shows Det. Nick Burkhardt (David Giuntoli) and Monroe (Silas Weir Mitchell) finding the elusive artifact that has been teased for many seasons. A key introduced early on in the show's run — one of seven that had been undiscovered until this season — was known to open something that was thought to be of monumental mystic importance. They've found that something 100 episodes in.

During the show's first season, L.A. Times TV critic Mary McNamara said of the show: "If there were an award for the new show that best sustained, and occasionally surpassed, the promise of its very well-done pilot (and I think maybe there should be), 'Grimm' would win, hands down." Five seasons in, the show has continually impressed with steady storytelling, and as its well-attended Comic-Con showings can attest, has captured the loyalty of its fan base.

We caught up with Giuntoli to talk about the 100-episode milestone, where the show has been going physically and plot-wise, and what's in store for the actor post-"Grimm."

When I talked to you years ago, you said you worship the law of low expectations. Reaching 100 episodes may not have been in view, but what does it mean for you and a show like "Grimm?"

People ask me what it's like to reach 100 episodes, but really, "Grimm" has always been a fighter. There are no movie stars on our show. We've never been a shoe-in. We've had to fight for our ratings and fight for our seasons.

We're kind of like a pitcher in the eighth inning of a no-hitter. If you get complacent, it can all fall apart. The experience of shooting 100 episodes ... well, it's not like we got picked up for five straight seasons. We had to earn each one of them. So I think when it's all over, when the game's over, I can luxuriate in our achievement. But until then, we're going to keep fighting, and it's the best thing about our cast.

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There've been major changes recently. Is this what needs to happen for this show — or with any show in general — to keep things interesting?

I don't think it has to happen with any show. At the end of Season 4, and the beginning of Season 5, there were some major changes, though. Some of our most-beloved sets were burned to the ground. The hero's woman became his big bad.

There were risks taken, and I spoke with Jim Kouf and David Greenwalt, our executive producers, and Jim just shrugged and said, 'Sometimes you have to take a chance and see if it works.' And they weren't being cavalier. I think that they just have the experience to know that sometimes you roll a six, sometimes you roll a two.

As long as you keep taking chances, that's where the fun is — and boy is it fun.

This season does seem like a lot of fun starting off. It's gone from supernatural procedural to action-adventure pretty quickly.

I really love the "Raiders of the Lost Ark" elements that are coming out. The developments on "Grimm" ... Nick and Monroe digging around in catacombs under an ancient church somewhere in Germany looking for treasure? It's so fun.

It's not that far removed from the world that our show started in: dark forests, fighting mythical creatures with axes and a hidden weapons trunk. These are very similar sensibilities. I think they work well together.

Speaking of working well together, the Juliette-Adalind-Nick relationship is ... weird. How did you take it when you knew that things would be heating up with your most bitter rival?

Well, they've certainly created a love triangle with the most possible drama — everything that you could possibly squeeze out of a love triangle.

I think the unexpected nature of the Nick-Adalind relationship threw people off and created camps: pro-Juliette camps and pro-Adalind camps. All you can say is kudos to the writing team.

Another kind of character development is getting out of Portland. With the city being such a part of the show, how does it feel to vacate — in the story — for a while?

Portland is strangely similar to Germany. I think that's really why, in fact, that we were able to have the show in Portland. The Black Forest of Germany looks very similar to the forest in and around Portland.

If fairy tales were ever real, they would be real in Portland or Bavaria. Dark, cloudy, verdant, overgrown, gnarled woods. If ever the big bad wolf were to live anywhere, it would be one of these two places. I'm surprised there aren't more direct flights to Frankfurt.

It's fun getting to buddy up with Monroe again [in the storyline]. I think the Nick-Monroe friendship is gold, and the fans love watching them interact. Monroe's light, exuberant personality, paired with Nick's very serious, taciturn personality — they play so well together.

As a lead actor on a show like this, under the radar but successful, how has the ride been?

One of the greatest regrets as an actor is that you're done with the audition or you're done with the scene, and you instantly beat yourself up. You're like, "Oooh! I should've done this! If only I had another chance." And you don't get another chance.

It's very rare that an actor gets so many opportunities between "action" and "cut." Most of your time as an actor is spent trying to get to that point, not living within those two points, and when you're on a long-running series, you have so much time in between those two moments to actually yell "cut."

So, I'm ever grateful for all of the opportunities I get to kind of change it up — fix things, better things, tweak things.

If we get a Season 6, it could very well be our last season, and it will be the first time that the writers would get to write to an ending. If we do, it'll be a very fun ride, with major events.

Well, here's the Peyton Manning question then: Do you know what you will do after that?

When you're an actor, you're conditioned to not look too far ahead. It's one season at a time for me. All you do is look forward to gearing up for that next fight.

It's usually something very personal to each actor. It's not as easy as "I want to do comedies." But you definitely want to create. Now that you see how things are done and you've been around directors for so long and producers for so long, you kind of understand the game a little more. Ultimately, you want to take more ownership, so I'd like to produce and direct. Anything where I can brood — on- or off-screen.

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