Of course, boasting about military strength is what you do to prevent war. But once war has started, you want to do the opposite -- you want to hide your true capabilities from the enemy, so they can't counteract them. So, for instance, during World War II the British were in that position of being the proverbial guy who has to convince the other guys he has a small dick.
"I need tweezers to masturbate."
During the Battle of Britain, the Germans started noticing that a crapload of their planes were getting shot down in instances where the British shouldn't have seen them coming. It was almost like they had some sort of radio device that could detect the presence of incoming objects -- actually, it was exactly that: Britain had perfected the radar and didn't tell anyone about it. Obviously the Brits couldn't let the Germans know they had access to this new technology, otherwise they could bomb the shit out of it or, even worse, try to create their own Nazi version. With the Germans getting increasingly suspicious, something needed to be done fast.
Britain's solution? Carrots.
British papers published a story about a RAF pilot called John "Cat Eyes" Cunningham who had shot down 20 enemy planes thanks to his superhuman night vision, an ability he achieved by eating lots of carrots. Other carrot-eating pilots followed, and soon the British government began publicizing the fact that carrots improve night vision -- which, of course, is complete bullshit. Carrots might help your vision not get worse, but they won't make it any better either. The pilots were winning the war thanks to radar technology, not by eating filthy plants.
Next - how bread crusts make your hair curly while actually it's just your terrible genes.
Still, the propaganda campaign worked so well that the British people began growing and eating their own carrots so that they could see better during the blackouts (running-into-walls related deaths went up 70 percent that year). The authorities knew they were lying, but it was all part of the ruse to fool the Germans. And as a result, some of you reading this had your mothers tell you to eat your carrots, because they were good for your eyes. All thanks to one bullshit propaganda campaign.
"Don't worry, our housewives are way better at picking out BS than the Nazi High Command."
The USSR's Stakhanovite Movement followed a pretty simple ideal: encouraging workers to over-achieve at their jobs out of love for the fatherland, by following the example of one great worker. The greatest Stakhanovites even received medals for "Soviet Valor" and were personally greeted by Stalin at the Kremlin.
Here's the thing, though: it was all bullshit.
The movement got its name from Aleksei Grigorievich Stakhanov, who in 1935 became a celebrity by breaking the highly specific record for amount of coal mined in 5 hours and 45 minutes with the winning total of... 102 tons.
If that sounds like a lot, you don't know that half of it. That's the equivalent of lifting the weight of three elephants per hour, or nine Honda Civics. One guy.
That's one elephant every 20 minutes, or the time taken for someone to Photoshop this.
Stakhanov's record exceeded the daily average for a normal, human minor by 1,400 percent, which meant he was clearly some sort of Russian Superman. Even the Americans were impressed by his coal-shoveling powers, as evidenced by the fact that he made the cover of Time Magazine.
"Cover story: Absolutely Fucking Nothing Happened this Week. Also Unicorns."
Of course, this was all part of a propaganda campaign: the mine was actually giving Stakhanov credit for the work of the whole mine, not just himself. Basically, by agreeing to become the poster boy for a new state campaign he was fucking his co-workers over, since they now had to follow his impossible standards once Stakhanovism became a thing. Anyone who spoke up against the unfair conditions was labeled a betrayer.
"You're supposed to work around the bodies."
And then shit got really stupid: a few months later, another worker called Nikita Izotov shattered Stakhanov's record by hewing 240 tons in the same amount of time, which at this point is 10 or 15 times what the real record probably was. It's like a guy claiming to have scored 1,300 points in a basketball game. And other sources claim it was actually 607 tons, but it might as well have been 5,000, since it was a fake record anyway. Basically, whoever could think of the highest number won.
Nikita Izotov, having just mined eleventy billion tons.
Stakhanovism found its way to other industries like automobile, textile, timber, railroad, agriculture and even shoe-making. Since the whole thing was Stalin's baby, though, as soon as the guy died all of it was officially declared bullshit.
Oh, North Korea. No list about crazy propaganda would be complete without you. So what did they do this time? Well, see for yourself:
In case you couldn't tell what was going on in that video (which would speak well of your mental health), that's North Korea's hit TV show Let's Trim Our Hair in Accordance With the Socialist Lifestyle (an actual thing), part of an ambitious propaganda campaign exclusively devoted to fighting the evils of long hair while informing people of the acceptable hairstyles. Here are two examples of state-sanctioned hairdos, as shown on Korean TV:
"These men are pictured from the neck up. Because they're chest deep in bitches."
According to the campaign, not only does long hair embody capitalism, it also decreases intelligence by robbing the brain of essential nutrients. Presumably they're not encouraging Koreans to completely shave their heads because a race of super-intelligent beings would be a lot harder to oppress. Men must keep a hair length between 1cm and 5cm, and must have it cut every 15 days. If they don't, they run the risk of being named and ridiculed on national TV.
You see, the campaign actually spanned several shows, one of which involved a fun reality TV aspect: hidden cameras would catch unsuspecting people whose hair did not fit the state's specifications, giving out their names and addresses as punishment. A North Korean equivalent of Ashton Kutcher would then come out and harshly confront them and demand explanations with a stern, disappointed expression. A lot of people would escape as soon as they saw him, possibly crying in fear.
"... and bitchin' sunglasses."
The campaign did allow men over 50 to have hair longer than 7cm so that they can hide their baldness (they are not monsters) while offering no justification whatsoever for Kim Jong Il's shameful past.
To be fair he didn't find out he wasn't a woman until he turned 41.
For more terrible pieces of propaganda, check out 6 Acts of Propaganda That Backfired Hilariously and The 17 Most Unintentionally Hilarious Propaganda Posters.