Holy shit, I'd never seen this clip before. It's Christopher Reeve (SUPERMAN) on "Late Night With David Letterman" from March 1, 1982, back when celebrities and hosts actually had real conversations of substance instead of going through the motions on a pre-tested set of shitty, hacky questions. Yeah, he was there to shill for a movie but he sure wasn't there to put Marlon Brando on a pedestal. At all.
The handsome Reeve, who was an ideal son of Jor-El, went from an unknown to Hollywood star virtually overnight thanks to the success of SUPERMAN, one of the top films of the superhero/comic book genre. Two years later, SUPERMAN II, most of which was filmed at the same time as the first one, was another hit. He was on Letterman to promote Sidney Lumet's DEATHTRAP and was still just in his late 20s but had no issue dumping on a certified legend.
But I don't think this was a case of a cocky, young actor showing no respect for a guy who helped pave the way for the actors that followed. He seemed genuinely offended that Brando took the $3.7M then threw up deuces on a huge-budget, long-awaited Hollywood production of one of America's most iconic cultural exports to the world. SUPERMAN was a big deal and Brando didn't give a fuck.
That disgusted Reeve so he let it be known on Letterman. He managed to do it in almost charming way, where he didn't come across as being an asshole. Because he wasn't being one, he was just giving us something we don't get from late night network shows anymore: genuineness. But damn son, he carved him.
By the spring of '82, Brando had no sway in a Hollywood that had essentially chewed him up and spit him out; he said he retired after his 1980 flick THE FORMULA flopped bad. So Reeve, coming off a pair of blockbusters, didn't need to worry about career repercussions from an old, wacky actor that no longer had the ears of powerful studio men. Not to mention, Brando already started to become a tabloid punchline by this time.
Also, that's an all-time Letterman line at the :47 mark. Fucking hilarious.
Interesting trivia: prior to filming SUPERMAN, the skinny Reeve refused to use muscle padding and instead went through intense workouts to fill out the iconic suit befitting a superhero. His trainer? David Prowse---better known as Darth Vader (though James Earl Jones voiced the iconic baddie).