"It is impossible, I think, for anyone to imagine 'The Tonight Show With Johnny Carson' without Ed McMahon," O'Brien said Tuesday during the NBC show.
"Ed's laugh was really the soundtrack to that show. For 30 years Ed played his part perfectly, he played it with effortless joy," said O'Brien, who took over the show from Jay Leno this month.
Sitting alongside Carson, McMahon was part of "the most iconic two-shot in broadcasting history. There will never be anything like that again," O'Brien said.
McMahon, who played second banana on "Tonight" until Carson retired in 1992, died early Tuesday at 86 after prolonged illness. O'Brien was 29 when McMahon was last on the show as Carson's sidekick.
Tuesday's show paid tribute to McMahon with highlights of his years with Carson.
NBC is owned by General Electric Co.
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