"Like The Beatles, Donovan developed a strong interest in eastern mysticism, and in early 1968 he traveled to India, where he spent several weeks at the ashram of the Maharishi in Rishikesh."-Wikipedia
I knew it! It is Donovan!
"He collaborated with The Beatles, contributing lyrics (and uncredited backing vocals) to the song "Yellow Submarine", which was recorded at Abbey Road Studios on 26 May 1966." -Same Article
Didn't Know that!
"I'd like to say 'thank you' on behalf of the group and ourselves and I hope we passed the audition!" -John Lennon during the Rooftop Concert
Isn't This Where We Came In?