Poor Cass, John Phillips didn't want her in the band, she couldn't hit the higher notes he wanted. In late 1964 or early 1965 Cass Elliot was walking down an alley in the Virgin Islands and was kathunked on the head with copper tubing dropped from a construction site. Cass was in the hospital for a short while and when she got out, those notes she couldn't hit before, she then could. But don't just take it from Johnny, take it from Cass:
It’s true, I did get hit on the head by a pipe that fell down and my range was increased by three notes. They were tearing this club apart in the islands, revamping it, putting in a dance floor. Workmen dropped a thin metal plumbing pipe and it hit me on the head and knocked me to the ground. I had a concussion and went to the hospital. I had a bad headache for about two weeks and all of a sudden I was singing higher. It’s true. Honest to God. --Cass Elliot in Rolling Stone in 1968.
Two final notes, note the audible reaction from the audience the first time they hear 'And no one's getting fat except Mama Cass'. Last, Cass died in London at No.12 at 9 Curzon Place, the exact flat where Keith Moon, drummer for The Who would die a little over four years later.
Oh, and the name of the Alley where Cass was walking that fateful day? Well, you know