The army drill routine is adapted from a popular sketch originated by Joe Besser, who would later join the Stooges.
After the US Congress passed the Selective Training and Service Act on September 16, 1940, comedies about military life became popular. "Boobs in Arms" was the earliest of its kind.
At 8 minutes 26 seconds, Curly takes what looks like an apple out if his pocket. Nothing is seen of the apple in subsequent scenes. Possibly it was a joke that was omitted in the editing process.
When the officer wakes up the sleeping stooges, Larry and Moe salute the officer. The pose that Curly makes is a reference to Benito Mussolini the Italian dictator at the time.