Bluto is seen here in a light blue sailor suit. He is also shown breaking the fourth wall, an unusual occurrence for the character.
Tom Ewell, best known for The Seven Year Itch (1955), is an audience member (behind the kid who gives Popeye the spinach) in the live action clip in the cartoon.
The "Spinach Killer" formula includes castor oil, DDT, and essence of skunk. At the time of this short, DDT insecticide was widely used and was actually marketed as being good for crops (and humans!)
The scene of a literal bowl of dust (The Dust Bowl) on the destroyed spinach farm was a reference to the catastrophic dust storm condition that swept the U. S. Midwestern farming region in the 1930's.