Harry Nilsson was friends with members of Monty Python.
George Harrison was a great pal of mine, and one night he came and asked if he could do the "Lumberjack Song" and we said, "Yeah, of course." So he came on stage at City Center, and he did the "Lumberjack Song" as a Mountie, and nobody knew it was George. Harry Nilsson found out George had done it and so the next night Harry is going to do it, but Harry’s pissed as a fart and makes a big display. "It’s Harry Nilsson." He’s waving and everybody’s looking at him like "Fuck off, Harry." He’s just supposed to be in the chorus. At the end of the "Lumberjack Song" everybody would step back and the curtain would come down, but Harry didn’t step back, he stepped forward, the curtain came down, and he fell off the stage into the audience and broke his wrist. Nobody ever recognized it was George, which was really cool and very typically George.
-- Eric Idle
George was wonderful. He came up on stage with us as a Mountie and sang the "Lumberjack Song" impeccably, and I don’t suppose 10 percent of the audience knew he was up there. And then Harry Nilsson came up and tried to take the show over, just one huge inflated ego. He wouldn’t do his Mountie’s jacket up properly, and insisted on wearing dark glasses. A Mountie in dark glasses? And then at the end of the show he started shaking hands with the audience and obviously just wanted as much attention as he could get. I was struck by the extraordinary contrast between George, who did it so beautifully and aesthetically, and Nilsson who was just a sort of egotistical drunk. It doesn’t mean that he wasn’t a nice chap, but under those circumstances he didn’t behave the way he should have done.
-- John Cleese
-  Graham Chapman, Michael Palin, John Cleese, Terry Gilliam, Eric Idle, Terry Jones. Thomas Dunne Books (2003-10-07) "The Pythons: Autobiography by the Pythons"
-  ibid