American actor Thomas McDonell, best known for his role as Finn Collins in the US television network CW’s post-apocalyptic series “The 100,” has a rather peculiar presence on Twitter.

One day in 2017, he made his first tweet in Korean. At that time, he was into tweeting in various languages to reach out to people from all over the world who were looking at his profile.

His tweets are usually simple expressions -- "I'm bored," "Is this for real?" -- in "banmal" the simplest and most informal form of Korean.

But over time his use of the language has become more natural and sophisticated.

Last year, a mention of Jungkook of K-pop phenomenon BTS even made entertainment news headlines in Korea. His tweet was, “Stop flirting with me Jungkookie,” written in Korean.

More than 90 percent of his recent tweets are now in Korean, which until a few years ago didn’t mean much to him.

“When Korean people started looking at me, and I started tweeting their Korean bios, something was different. Koreans really responded to an American tweeting in Korean,” McDonell, 37, said in an interview with The Korea Herald.

“I think Korean people’s attention to my Korean tweets has to do with the cultural and political history of Korea and the US -- how for a long time the gaze of the world was to the West, to the US, and how recently, that gaze has been shifting in particular toward Korea,” the actor mused.

“I think this is the meaning of Hallyu, or the Korean Wave.”

In the beginning, McDonell just copied some words or phrases from tweets written in Korean. As Korean letters seemed like artistic lines and curves to him, rather than recognizable letters of a language, his selection was largely based on how attractive their shapes were.

After discovering Korean films and music, his interest in the language deepened and he buckled down to study the language.

“I’ve mostly studied Korean on Twitter and at museum exhibitions. And for a while I had a tutor whom I met online while I was living in Texas filming a war movie,” he said.

The actor said just two nights prior, he had watched Korean director Park Chan-wook's latest feature film “Decision to Leave.” “It was fantastic. And I’m going to see ‘Broker.’”

“Broker” is the first Korean-language film project by Japanese auteur Hirokazu Kore-eda and features a cast of well-known Korean actors, including Song Kang-ho, Bae Doo-na, Gang Dong-won and Lee Ji-eun, better known as singer IU.

After five years of tweeting in Korean and some years of language study, McDonell says he now understands daily conversation in Korean and can read plain Hangeul, the Korean alphabet, on Twitter.

His favorite Korean word is “sam" as it carries more than one meaning.

“It means three, like the number, and also can refer to hemp, like cannabis – what a lot of people in the US call ‘weed,’” he said, adding that many American learners found this interesting. “I see on the news that there have been a lot of high-profile weed crimes in Korea lately as well.”

Aside from the language itself, he has always been intrigued by the history behind Hangeul.

“Korean is an elegant, ergonomic language. The most interesting aspect of Hangeul is its efficiency and the story of how it was created,” he said.

The writing system was introduced by King Sejong in 1443 to promote literacy among common people. The educated elite at that time were using classic Chinese characters, which reinforced their monopoly on knowledge and learning.

“I visited Korea once with my friend. I learned a lot on that trip about the language but especially about the culture. I want to make a film in Korea. I’d love to come back soon,” he said.

McDonell's film debut came in 2008's “The Forbidden Kingdom," starring Jackie Chan and Jet Li. In 2021, he appeared in an episode of Emmy-winning NBC musical comedy TV series “Zoey's Extraordinary Playlist.”