During WWII, the US government financed a series of Private Snafu cartoons. Using a wonderful sense of humor, they were able to convey important messages to the troops--and the films were not shown to the general public. You can tell this in a few of the films, as the humor is a bit more adult than you could have gotten away with in theaters. Today, you can find these shorts on DVD as well as for free downloads at archive.org.
Interestingly, I've noticed that there were different directors for the Snafu films. In this case, it's Friz Freleng--of Looney Tunes fame. Not surprisingly, the film looks exactly like a black & white Looney Tunes film--and the effect is heightened by the familiar Looney Tunes music by Carl Stalling. And, the film is narrated by Robert C. Bruce--a guy who narrated tons of cartoons for this same company! With all this excellent talent, it's no surprise that the film is cute and enjoyable--and gets the message across that the troops need to be vigilant against mosquitoes and the illnesses they transmit. It's done in a clever way--showing the bugs going through basic training just like people--and only the finest and most virulent are chosen! While Snafu only appears at the very end, it's worth watching.