In what is almost certainly the largest audience that has ever tuned in for a television appearance by the curator of the Leavenworth Nutcracker Museum, the debut of “Conan,” the new late-night show starring Conan O’Brien, got off to a strong start Monday night. In his first outing on TBS at 11 p.m., Mr. O’Brien (who, you may have heard, had a network gig before moving to basic cable) drew an estimated 4,155,000 viewers, according to TBS.

That number easily bested shows hosted by Mr. O’Brien’s cable-television frenemies Jon Stewart, whose “Daily Show” on Comedy Central was watched by 1.3 million viewers, and Stephen Colbert, whose “Colbert Report” drew 1 million; it also put Mr. O’Brien ahead of his network nemesis Jay Leno, whose “Tonight Show” was watched by 3.5 million people on NBC, and his “Late Night” predecessor David Letterman, who nabbed 3.4 million viewers for his CBS “Late Show.”

TBS had to be pleased with the demographic breakdown for Mr. O’Brien’s audience, which skewed young: 2,451,000 viewers aged 18 to 34 and 3,285,000 viewers aged 18 to 49 watched his first broadcast, which featured appearances by Seth Rogen, Lea Michele, Jack White and Arlene Wagner of that aforementioned museum.

Though that lineup may be hard to beat, Mr. O’Brien will try to top it on Tuesday night with Tom Hanks, Jack McBrayer and Soundgarden.