A funny thing happened on the way to the State Fair grandstand. Dennis Miller’s old “Saturday Night Live” boss showed up Thursday night — Sen. Al Franken.

In the middle of his stand-up set, Miller recognized Franken’s laugh in the crowd. Then when Miller, America’s most intellectual right-wing comic, started cutting up Vice President Biden, he quipped: “I don’t hear Al laughing anymore.”

Miller and his fellow “SNL” alums Dana Carvey and Kevin Nealon kept a sparse crowd of 2,863 laughing for nearly two hours.

Looking out at all the empty green seats, Miller, 59, observed: “The last time someone played in front of this much green, it was Carl Yastrzemski in 1967 at Fenway Park.”

Miller’s 25-minute set was packed with pithy punchlines, rapid-fire rants and a barrage of big words like rivulets, mammular and veritable. He made fun of Finland, aging rock bands (“Rip Van Halen”) and Nancy Pelosi. He knows how to walk the line; on the list of pressing issues facing our country, he said gay marriage is the 8 billion and 45th — “right ahead of global warming.”

Knowing that trying to follow motormouth Miller and all his big thoughts is a challenge, Carvey walked out with an acoustic guitar, offering to a sing an obscure Neil Young song called “Minnesota State Fair.” In perfect Young voice and cadence, he sang with Neil-like simplicity: “Went to the state fair, oh yeah/ Had a corn dog there/ Had a corn dog there/ saw sluts on the Tilt-a-Whirl …”

Carvey, the master impressionist, instantly changed the mood. For the next 25 minutes, he went through his repertoire — the Church Lady very briefly and then a cavalcade of presidents, effectively showing how George W. Bush or Bill Clinton would say something and how Barack Obama would express the same notion with his high-minded verbiage.

Carvey also did impressions of his parents, his teenage sons, Sean Connery, a drunk pilot on Ireland’s Aer Lingus and his cardiologist of Indian descent. Just as the 58-year-old seemed to be hitting his stride, his set came to an end.

Nealon, 59, who had the longest run on “SNL” from 1986-95, opened the evening with a strikingly conventional stand-up routine. He made lame jokes about getting older, concertgoers arriving late (“you missed Dana and Dennis”) and helping his wife deliver their recent baby. His best stuff was when he reprised his old “SNL” habit of making a statement and then, in a softer voice, making a negative comment. For example, “You’re from Columbia Heights,” he said to a concertgoer. “They’ve got nice houses there … trailer park” or “I bet you’re a good dad … Charlie Sheen.”

After the individual sets, the three former “SNL” colleagues — two “Weekend Update” anchors and one impersonator — sat on stools and entertained questions from the audience. In this spontaneous session, these three underemployed veterans were in their element, riffing off one another, dusting off old bits or making fun of the questioners. And sometimes they just gave straight answers.

Inquiring minds wanted to know about favorite musical guests (which gave Carvey a chance to do his Paul McCartney), if they would consider going back to “SNL” (“It’s a kids’ game,” Miller said) and if Carvey would sing “Chopping Broccoli” (he did a little bit and asked the questioner to sing it, too).

Fans, most of whom seemed to be under the age of 30, asked about the “SNL” bosses, Lorne Michaels and even Franken, who worked his way up from writer to producer.

“Franken was my first boss,” Miller said. “He was brutal. He’d say, ‘This is a [crappy] joke. You need to write a funny one.’ He was a great boss.”