August 22, 1968 Ringo Starr temporarily "quit" The Beatles. After walking out on a recording session that day, he took a trip to Sardinia, where he borrowed a yacht that belonged to his good friend, actor Peter Sellers.
While he was gone, Ringo wrote Octopus's Garden. The band tried to continue recording without him, but soon realized they needed him, so they sent him a bunch of telegrams. After about 2 weeks, Ringo finally returned to Abbey Road.
Here is some video footage of the band in studio working on the song.
Here's another clip of Ringo Starr talking about leaving and returning with Conan O'Brien on a panel in Los Angeles back in 2015.