The Thimble Theatre created by cartoonist Elzie Segar debuted on December 19, 1919. The King Features strip was designed as a replacement for Ed Wheelan's Midget Movies (he had moved on to create Minute Movies). The original strip parodied popular movies and plays of the time.
The two central characters were Castor Oyl and his pal, Ham Gravy. In case you have not guessed what is coming Castor had a sister named Olive. All three appeared together for nearly 10 years until on January 17, 1929 a new and now very familiar character made his first appearance. Castor Oyl and Ham Gravy were down at the docks and as Don Markstein tells us:
"'Hey there! Are you a sailor?' Castor called to a one-eyed man wearing a nautical outfit, with an anchor tattooed on his arm.
'Ja think I'm a cowboy?' said Popeye, who at that moment became an integral part of the Thimble Theatre cast. Within a year, Ham was written out of the strip and Popeye replaced him as the sweetheart of Castor's sister, Olive. Wimpy was added to the cast in 1932, and Swee'pea in 1936."
And rest is history :)