The "S" from the spinach can lands on Popeye's chest, turning him into Superman. A cheeky bit of cross promotion. The Fleischer Studios had recently premiered the first Superman cartoon.
The hypnotist was voiced by the versatile Jack Mercer.
The sign "Professor I. Stare, 10¢ a Trance," is a pun on the taxi dance halls of the era, where hostesses offered a dance for a 10¢ ticket.
Popeye tries to woo olive Oyl by giving a variation on the famous line from Romeo and Juliet, "What's in a name? That which we call a rose, by any other name, would smell as sweet."
This short was released just after the U.S. entry into WW2.