During WWII, the film studios went into full patriotic mode-- churning out tons of films supporting the war effort. So it wasn't at all surprising that they'd also create cartoons which featured barely human Germans and Japanese characters being foiled by the likes of Bugs Bunny, Donald Duck and Popeye. However, this created a huge problem after the war when we were suddenly allies with these same nations and it was no longer fashionable to hate them! Add to that, modern political correctness and it's not at all surprising you never films like "You're a Sap, Mr. Jap" on television these days! While I certainly can understand this, I am glad you can find them on YouTube and hope they're also available on DVD as this IS a part of our history.
In this particular film, one of many Popeye films about the war, our hero is doing something VERY unusual for Popeye--he's flying a plane off an aircraft carrier! In a cute scene, a hidden Japanese plane comes upon him...and Popeye doesn't recognize it at first because it's disguised as a cloud. Soon, however, Popeye goes to work-- first beating the snot out of this pilot and then landing on a Japanese battleship and thrashing everyone. The Japanese are very stereotypical--sporting HUGE teeth and at the end are compared to rats! Subtle, it sure isn't...but it is entertaining, funny and did the job in helping drum up support for the war at home.