It was the summer of 1945, and things weren't going well for the Japanese. Their only remaining chance of victory was to deliver a truly devastating knockout blow to the Allies. Such an important last-resort move could not be trusted to just anyone, so naturally the Japanese military turned to a bona fide mad scientist.
While we're sure he wouldn't have described himself as "mad" (so few evil scientists show that level of self-awareness), the evidence disagrees: Shiro Ishii served as the head of Unit 731, a covert biological warfare research team, and there really is no positive way to spin that kind of thing, is there? There was no "covert biological warfare research team" whose primary goal was to produce the fluffiest bunnies the world had ever seen so all the troops would stop fighting and start snuggling.
"We tried that with the Lennie Project. It failed."
No, mysterious biowarfare units generally pull crazy supervillain-level stunts like breeding millions of fleas infected with the plague to release them on their unsuspecting enemies. Which is exactly what Ishii planned on doing, incidentally.
One of Japan's fancy new aircraft-carrying submarines was supposed to surface off the coast of San Diego one night and launch three planes. The aircraft would release special ceramic bombs that shattered as they fell, unleashing hordes of Ishii's plague-minions over the city and devastating the area. Out of other, saner options, Japanese higher-ups gave their blessings and dubbed it Operation Cherry Blossoms at Night. Hey, in wartime, you have to create beauty whenever you can -- if only to balance out the horror (of plague-infected flea bombs, for example).
Operation Itchy Dog Ass didn't inspire as much pride.