First appearance of Claude Cat.
First appearance of Hubie and Bertie.
A half grapefruit was a popular breakfast dish at the time. Jimmy Cagney also famously smashed one into the face of Mae Clarke in the 1931 film Public Enemy.
Claude is seen prowling on all fours, like a traditional cat, as well as walking upright.
The author of the first book Claude reads is F.E. Line, a play on the word feline.