Over the last few years, Mitch Glazer, the screenwriter and producer, has watched with awe and bewilderment what has happened to Bill Murray.

Mr. Glazer has been friends with the actor for decades, and they have worked together on several projects, including “A Very Murray Christmas,” his Netflix holiday special having its premiere on Dec. 4. Mr. Murray first gained notice during his “Saturday Night Live” days in the late ’70s before shooting to stardom with the 1984 comedy “Ghostbusters.” But in the recent past, his fame transcended mere Hollywood celebrity.

“It’s the feeling of how they make crystals,” Mr. Glazer said. “It’s water, it’s water, it’s water, and then it reaches this density, and all of a sudden, it’s this other thing.”

What Mr. Glazer means by “this other thing” is the transformation of Bill Murray the actor into a pop icon.