By Dean Robbins

America’s favorite late-night host was a mystery man

Johnny Carson hosted “The Tonight Show” for 30 years, inviting himself into American homes with the salutation “Heeeere’s Johnny!” An “American Masters” profile (Monday, 8 p.m., PBS) begins with fellow stars praising Carson in familiar ways. He had the best jokes; he had a gift for making his guests look good; he had universal appeal. Well, OK. But just as you’re about to change the channel, frequent guest Joan Rivers calls Carson “a tough, aggressive killer.” Bandleader Doc Severinsen admits to being intimidated by him. Acquaintance Carl Reiner acknowledges his standoffishness. Now this is getting interesting.

As a budding Nebraska entertainer, young Johnny Carson was obsessed with magic, and he continued to create illusions when he became TV’s biggest star in the 1960s — specifically, the illusion that a shy loner was everybody’s best friend. When the cameras stopped rolling, however, he was a mystery man, even to his closest family members. If there’s a Rosebud in this “Citizen Kane”-like inquiry, it’s Carson’s disapproving mother, who never found him worth all the fuss and said so publicly.

The “American Masters” portrait gives Carson his due as an artist while investigating the chill in his soul. Only Johnny’s mother could fail to find it compelling. CV