"You were handed the baton by one of the all-time greats. But once it was in your grasp, you ran the race," Crystal said. He and Leno, longtime friends, reminisced about the old days, with Leno recalling how Crystal and other comedians visiting his town, Boston, stayed in Leno's apartment.
"You're calling it an apartment. I'm calling it a bomb site," Crystal joked.
Leno told how he was poised to make his network debut on Dean Martin's show in 1974 when news came that President Richard Nixon had resigned in the Watergate scandal. Leno's appearance didn't happen.
"Making me the last guy screwed by Nixon," Leno said.
Garth Brooks performed his touching song "The Dance" before Leno's likewise touching farewell remarks.
"Now that I brought the room down," Leno joked, he asked Brooks to lighten it up. Another Brooks' song "Friends in Low Places" closed out the show.
Leno, 63, has said he plans to continue playing comedy clubs, indulging his passion for cars and doing such TV work as comes his way — other than hosting on late-night.
"I'm real excited for Jimmy Fallon," Leno told his audience. "It's kind of fun to be the old guy and sit back here and see where the next generation takes this great institution."
AP writers Lynn Elber and Derrik J. Lang contributed to this report.