In the original commic, the whiffle hen would magically enchant anyone who scratched it on the head; most people got supernatural luck, while Popeye got super-strength.

In fact, in the story in which he debuted, Castor Oyl hired him to bring the group to an island casino to swindle the place using Castor's boosted luck. Popeye used his strength to beat the shit out of some thugs who chased them back to get their boss' money back; it also saved Popeye's life since the boost also let him survive being shot six times.

Interestingly, Popeye debuted ten years into the comic's storyline - it was originally called Thimble Theatre and Olive Oyl was the main character; but she later dumped her fiancé Ham Gravy to date Popeye.

Also, the whiffle hen's magic ended up permanently imbuing into Popeye, making him superhuman. The spinach thing was added later because he needed it as a psychomatic crutch to get his strength back.