Spoilers ahead for Thor: Ragnarok. Films in the Marvel Cinematic Universe are known for having pretty excellent cameos meant to connect films in different franchises. For example, Chris Evans (Captain America) appeared briefly in Thor: The Dark World. But the cameos in Thor: Ragnarok are more for fun than for MCU continuity. Case in point: the Matt Damon cameo in Thor: Ragnarok is 100 percent pure fun. No, Damon isn't joining the MCU as a superhero, but he does have a pretty awesome role in the third Thor film, out now.
Damon appears towards the beginning of the film when Thor returns to Asgard after a long time away. Presumably, Thor hasn't been back since the end of The Dark World, when he unknowingly left Asgard under the rule of his trickster brother Loki. Asgard, it seems, is not as he left it. Heimdall has been convicted of treason, and King Odin (aka Loki in disguise) sits on a thrown watching "The Tragedy of Loki," a play that portrays Loki's heroic death, as seen in the Thor sequel. Of course, Loki wouldn't let just anybody play himself, so he has chosen someone who looks an awful lot like one of America's most beloved movie stars, Matt Damon. Wearing an impressive black wig and Loki's signature green robes, Damon plays Loki in the surreal play. He's only on screen for a minute or two — who knows if his unnamed Asgardian actor survived Hela's murderous arrival — but it's definitely long enough to earn a place in MCU cameo history.
Rumors of Damon's Thor: Ragnarok cameo began to swirl in September, and, though he did not confirm his appearance in the film, the actor did attend its premiere in early October. Knowing now that he is actually in the film explains his walking the red carpet. It also might help explain why he "crashed" Chris Hemsworth's interview on Jimmy Kimmel Live on Oct. 10. During Hemsworth's interview promoting Ragnarok, Damon highjacked the segment, appearing alongside Ragnarok star Mark Ruffalo and director Taika Waititi.
"Why are you friends with him?" host Jimmy Kimmel asked Hemsworth, to which the actor responded, "I feel sorry for him... He has nothing, he has nothing." At the time, the gag seemed like an opportunity for Damon to promote his new film Suburbicon, but it looks like it might have been foreshadowing his Ragnarok cameo.
As for how Damon came to have a cameo role in Thor: Ragnarok, that question can be answered pretty easily. It turns out that Damon has been friends with Thor himself for years. When he's not busy being one half of Hollywood's most famous bromance (Matt and Ben forever), Damon might be found traveling to Australia to visit his pal Hemsworth. In fact, the two mega-stars have been friends for years. "We became friends around the time I started to work, and I've really benefited from watching how he handles himself," Hemsworth said in a 2014 interview with GQ that actually took place at Damon's Los Angeles home.
Unfortunately, it looks like this might be the end of Damon's journey into the MCU. The actor has shown little interest in joining any superhero franchise (it helps that he's already the star his own action franchise as Jason Bourne), and what interest he has shown has been very specific. While promoting The Martian in 2015, Damon told the New York Daily News that he'd consider playing a superhero it "if the right thing came along." He also admitted that he'd always loved Daredevil, a character who exists within the Marvel cannon. However, that role has already been taken by Charlie Cox in the Daredevil Netflix series. And now that he's officially an Asgardian in the MCU, it's unclear whether or not Marvel would recast him in another role. But, hey, there's always DC.