Aquaman star Jason Momoa surprised anyone lucky enough to attend the premiere of DC’s newest movie by leading a haka—a traditional Maori dance. It’s a ritual that’s well known to anyone who lives in New Zealand or follows their sports, but may be less familiar to those of us who live in the United States or Europe.

So, what is a haka? The haka, as it’s most commonly understood today, has its roots in Maori tribal warfare. War haka were performed before battle to intimidate the enemy and energize tribal warriors. Many of the movements seen in haka still have many of these qualities—performers may widen their eyes, stick out their tongues, stomp their feet and slap their chests, all while loudly chanting. Today, haka are often seen performed at sporting events, particularly involving New Zealand teams. The New Zealand national rugby union team is probably the most famous for it, and continue to perform the haka before international matches, but other teams and sports have adopted the practice as well.

Yet, while the haka can look intimidating, that’s no longer the point. Along with sporting events, you’ll also see haka performed at weddings and funerals, and for special guests as a show of respect. It’s an important part of the Maori culture, that more than anything is a celebration of life and our world. That’s likely why Momoa and his crew chose to perform one at the Aquaman premiere. He was joined by his children and by actor Temuera Morrison, who plays Aquaman’s father in the film and is from New Zealand.

You can check out the haka below!

Aquaman arrives in theaters on Friday, December 21, 2018. For more on the upcoming DC blockbuster, click here.