The U.S. Marine Corps was so flattered that Bugs Bunny decides to become a Marine in this film that it insisted he be officially inducted into the Corps as a private, which was done, complete with dogtags. Bugs was regularly promoted until he was officially "discharged" at the end of World War II as a Master Sergeant.
The rabbit-hating cowpoke sounds like an early Yosemite Sam, whose character debuted a few years later
The Overstreet comic book price guide credits the comic book adaptation of this short as featuring the very first "funny animal superhero" in the history of comics.
The newspaper story seen below "Cottontail Smith to Rub Out All Rabbits" had nothing to do with a rabbit drive. It appears to be a 1939 preview of the 1940 US election. The story erroneously predicted that Vice President Garner would be retained as Roosevelt's running mate, but correctly predicted that Republicans would choose a "dark horse" candidate to run against him. The candidate was industrialist Wendell Willkie, who had never held public office.
As chemicals flow through the winding test tubes, the catchphrase "Eat at Joe's" can be seen.