This is a good cartoon, and a good example of wartime humor - which by 1943, when the war was really beginning to bite back home in the US, had quite an edge.
The phone booth gag is "Is that you, Mert?" a fossilized gag phrase from the period, taken from "Fibber McGee and Molly". It was a catch phrase that audiences of the period would react to as a conditioned response. If you like old cartoons, it helps to be familiar with old-time radio of the period, because the cartoons mined radio for gags constantly (and Mel Blanc was a star in both, as a regular on the number one-rated Jack Benny show). The cartoons are full of show catch phrases, advertising slogans, and caricatures of movie and radio stars and minor characters.
The pinup picture is startling. I remember glimpsing it on my VHS copy and grabbing the remote to rewind and slow-motion. It is quite explicit, and seems like it could have got Friz Freleng in hot water at the time. You can see on the back wall at the first appearance of "Shulz", when he marches across the bunker floor to report.
For real unvarnished Freleng/Warner Brothers wartime humor, check out the "Private Snafu" series, which were intended for distribution to the troops only.
