After some time in improv and various acting troupes, Yeun achieved his mainstream breakout with The Walking Dead. In the show, he played Glenn Rhee, who was introduced in the 2010 pilot and was killed off in 2016. While on the show, Glenn was marked by being “the heart of the show”, according to former showrunner Glen Mazzara.  

Glenn’s death prompted an outpouring of fan support and retrospectives on his character and his positive role in increasing representation for Asian Americans. Benjamin To writes in an emotional eulogy for the character: 

“The mere existence of Glenn Rhee was revolutionary. Here was a bright, young Asian-American male character on a mainstream American television program who served a greater purpose than just existing solely to be a sidekick or a punch line to a second-rate joke. He was a loyal friend, a fearless leader, and a loving husband. The complexities behind the portrayal of Glenn elevated his character above Long Duk Dong, Leslie Chow, and Han Lee. He was fully-fleshed and multi-faceted. He had different shades, wrinkles, and nuances, resembling more a relatable human being rather than a cartoonish caricature.”

In an episode of Ugly Delicious, hosted by David Chang on Netflix, artist David Choe indicates that it is unusual and culturally significant for a Korean American man/white woman to have a sexual relationship on television, referring to Glenn and his white wife, played by Lauren Cohen. [add in particularities about Asian American heterosexual desire for white women → indicating assimilation and ‘white proximity]. 

Yeun’s own reaction to his portrayal and departure were more complex and contradictory. Upon his entrance to the show, Yeun found himself having to immediately challenge his portrayal. 

“In the beginning, the first couple episodes, Glenn was human, but he was also very expected. There’s a reason why the first costume designer had me wear Short Round clothes, you know? … [The costume designer] was like, ‘Here’s a thing that I picked out, and it looks just like Short Round. Here’s a Japanese flag that we want you to wear.’ And in my head, I’m like, ‘Why would I choose that?’ I could choose that, but why would I choose that? And it’s just that type of pervasive starting point.” Indiewire, 2018

Here, Yeun immediately foregrounds his own subjectivity as an Asian American actor - questioning the mode of representation and default images of Asian Americans - but also the subjectivity of the character, a Korean American who is fully embedded in Atlanta. 

Speaking more on his departure from the role, Yeun was mixed. He appreciated the mentorship of Andrew Lincoln, a theme that continues through his career. Yeun always remains vastly committed to peership and collaboration, frequently citing the musings of Director Lee Chang dong and Boots Riley as sources of inspiration; in other words, Yeun rejects auteurship or individuality in his performances. However, with a couple years distance between The Walking Dead and his current film career, Yeun finds that producers and audiences have limited his character. Speaking with Vulture, he says “I might not be objective, but I truly feel like people didn’t know what to do with Glenn. They liked him, they had no problems with him, and people enjoyed him. But they didn’t acknowledge the connection people had with the character until he was gone.”

In another interview with Slate, Yeun further elaborates that his character felt stilted, especially in terms of expanding the idea of what Asian Americans could be: “I felt beige with Glenn. That was a little bit of the frustration that I could never explain to the wider society, to fans of the show… I felt cramped. I felt like there wasn’t space for me to fully spread all of who I was, and that was partly due to me, too, because when I started, all I was trying to do was to work within the parameters that they were giving me. And then, over time, I just outgrew it. That’s why it was beige. Because he was meant to be the heart of that show. When you look back, you go, “That’s great, everyone wants to be represented that way. Why wouldn’t you want to be a perfect being?” But I don’t wanna [play] perfect, because we’re not perfect. And that’s a thing that I wasn’t able to feel for a while, because I was holding up this ideal that was way bigger than me, way larger than any single human can possibly do. I became less and less interested in doing that.” While this explains his departure to more nuanced and darker roles almost immediately after leaving The Walking Dead, Yeun also gestures towards the Model Minority and quiet, politically inactive Asian American stereotypes.