I mean, they set up that line as a joke, an actor cursed with his own success to repeat the same fucking line over and over and over. It could have easily been a one-note punchline, the catchphrase that made the creator cringe.
But it is because of his success that the line takes on a meaning for all the fans, inspiring a generation of followers to live better lives and engage with the community they love. So he must endure the cringe, because it pays the bills.
And then someone takes it seriously. Like, they create the thing he imagined, and now the line is fucking real. Real people (aliens) believe in Grabthar and Warvan, and truly believe that it means something to swear by Grabthar’s hammer and the sons of Warvan. And it’s Alexander’s worst fucking nightmare, because he can’t say it was all made up. Lives depend on believing their shared fiction. He must endure the cringe or people will die.
And then someone does die. Quelleck lived his life by the fictional code of the Mak’Tar, because he believed with all of his soul that it was the honorable life worth living. And it wasn’t religion or revelation, it was just Alexander’s acting, the role he embodied, playing out on an old tv show. That formed the basis for Quelleck’s life, and now that life was being sacrificed.
Alexander looked into Quelleck’s eyes and said the fucking line, because for the first time, maybe ever, he actually meant it. It was the greatest, and final, moment of Quelleck’s life. It was real. It wasn’t acting, it wasn’t art, it wasn’t a job. Dr. Lazarus stood up and avenged Quelleck.
Galaxy Quest was a much better movie than it had any right to be.