I found the term “that guy”, used as “He embarked on a career as a 'that guy',” in the following sentence of the article of the New Yorker (Feb. 7, 2011) titled “the Most Interesting Man in the World”:
In a recalls of a contentious exchange with Hoffman: “I jumped up and said, ‘Dustin, the reason you don’t like me is because I’m gonna make it and you’re not.’ ” Jonathan Goldsmith eventually made it - out to Los Angeles, anyway—and embarked on a career as a “that guy,” very often the that guy who gets killed, on television shows such as “Bonanza,” “Mannix,” “Gunsmoke,” “Hawaii Five-O,” ... to name a few.
As I don’t understand what that guy used in quotes means, I checked online dictionaries. Neither Cambridge online, nor Free Merriam-Webster has an entry for “that guy.”
Only Onlineslangdictionary.com carries the definition as “any person who does something considered inappropriate,” with an example, “I was going to crack a joke then, but I didn't want to be that guy.” But I don’t think this definition applies to “that guy” appearing in the above sentence.
What does “that guy” as a career Goldsmith built up mean? Does it mean a villain (in the film)? Is "that guy" a well-received of its own word?