And “30 Rock’’ star Tracy Morgan appeared in a flashback from a pioneering 1950s sitcom that featured African-Americans — a spoof of “Amos `n’ Andy’’ with a burnt-cork-faced Jon Hamm as his black sidekick.

Among other surprise guests were Amy Poehler, Jimmy Fallon and Fred Armisen.

Thursday’s episode was the second such venture for “30 Rock,’’ which aired live the first time in October 2010. As it did then, this half-hour was broadcast from NBC’s Studio 8H — otherwise the home of “Saturday Night Live’’ — in front of a live studio audience.

The initial performance — telecast at 8:30 p.m. Eastern time — went smoothly, with no noticeable technical glitches and one minor flubbed line.

Three hours later, the cast and guest stars hit their marks once again for viewers in the western U.S. One change: instead of Sir Paul, reality queen Kim Kardashian made use of Donaghy’s bathroom.

By the end of the episode, Donaghy was won over to the importance of live TV.

“`TGS’ is meant to be live,’’ he concluded. “To make it more profitable, we’ll just need to do more sponsored product placements. Or I’ll just pay you all less.’’

Whereupon Paul McCartney reappeared on stage, looking dazed.

“I slipped and hit my head in the bathroom,’’ he said. “Who am I?’’

“You’re my boyfriend!’’ Liz Lemon told him as she gleefully led him away.

In the western version, Kardashian had the last word. When Liz remarked that 2.5 million viewers saw “TGS,’’ Kardashian strolled by and recorded the moment on video for her followers.

“Now, 14 million people just saw it. You’re welcome,’’ Kardashian said. “Oh, and also, I broke your toilet.’’

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Online:

http://www.nbc.com

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AP Television Writer Lynn Elber in Los Angeles contributed to this report.

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