The Beatles - "Yellow submarine"

This was used as the B-side of "Eleanor Rigby."
Paul McCartney wrote it as a children's story. The story goes that Paul was lying in bed late one night, and an idea popped in his head to write a children's song - the actual song may have been a spin-off from Bob Dylan's Rainy Day Women #12 And #35." Paul purposely used short words in the lyrics because he wanted kids to pick it up early and sing along.
Ringo sang lead, as he did on many of the lighter Beatles songs, including "Octopus's Garden" and "Act Naturally."
The sounds of bubbles, water, and other noises were recorded in the studio. John Lennon blew the bubbles through a straw, George Harrison swirled water in a bucket. The vocals were sped-up to make it even more quirky. Vocals of the submarine crew are John and Paul in the studio.
Some people felt this song had deeper meaning about drugs or war. The Beatles said it did not, but they were used to people reading too much into their songs. On The White Album, there is a song called "Glass Onion" that addresses this issue.
The chorus at the end consists of the studio crew, as well as their friends Mal Evans and Neil Aspinall, producer George Martin, and Patti Harrison.
According to Steve Turner's book A Hard Day's Write, about a month after the album was released, there were barbiturate capsules that started to be known as "yellow submarines." McCartney denied any comparison to drugs and said the only submarine he knew that you could eat was a sugary sweet he's come across in Greece while on holiday. These had to be dropped in water and were known as "submarines."
After he got the idea for the song, McCartney dropped by Donovan's place and asked him for suggestions to close the tune. Donovan came up with "Sky of blue, sea of green." Donovan went with The Beatles on their retreat to India in 1968.