Superman is a superpowered crimefighter created by Jerry Siegel and Joe Shuster in 1938 who, like Popeye, has been called "the world's first superhero", and whose powers are in many ways similar to the comically strong sailor's feats. Both characters also have in common the fact that Fleischer Studios first adapted them from comics into animation. Eventually, they even had encounters with parodies of each other in their respective settings.
The Famous Studios cartoon short She-Sick Sailors from 1944 has Olive Oyl enamored with the Superman character, to the point that she rejects Popeye's attention. Bluto takes advantage of this by disguising as the superhero, shaving his beard and donning Superman's red-and-blue costume. He uses tricks to pass himself as Superman, such as "stopping" a train at the station and employing a bullet-proof vest in order to withstand machine-gun fire. Popeye turns into a superhero version of himself upon eating his spinach, enabling him to defeat the false Superman and save the endangered Olive.
Olive is seen actually reading Superman comics in the beginning, with her house adorned with Superman posters and memorabilia.
DC Comics, the publisher of Superman, in turn introduced their own affectionate parody of Popeye, calling him "Captain Strong". He first appeared in Action Comics #421 (1973), and was meant to resemble Popeye but in a more realistic style of drawing that would suit DC's more serious superhero comics. His inspiration however was clear, with his odd-looking face, manner of speech and such supporting characters as his fiancee Olivia. He would also gain strength from eating a vegetable, this time a type of seaweed that, unbeknownst to him, was of alien origin.
After their first encounter, Strong would become friends with Superman - and also with his alter ego Clark Kent. He would go on to make a few further appearances in DC Comics publications over the years.