A bit late on this, but still:

On February 7, 1910, a group of foreign dignitaries -- Abyssinian princes conducting an extended tour of England -- arrived at the docks at Weymouth. They had arrived with the intention of inspecting HMS Dreadnought, the most formidable warship on earth, and to pay their respects to her crew and commander. Her captain at the time was Herbert Richmond, a prickly and unpopular character in the Navy, but one who could be counted on to observe the proper niceties in a situation such as this.

Their arrival was not unexpected -- Herbert Cholmondeley, a clerk of the Foreign Office, had telegrammed in advance to warn the Dreadnought and her crew of the dignitaries' imminent arrival. Their Abyssinian provenance threw everyone off kilter; protocol demanded an honour guard and a formal reception in a case such as this, but the notice of their arrival had been so short that no Abyssinian flag could be acquired. It was consequently decided (somewhat bafflingly) that the flag of Zanzibar would be flown instead, and the Zanzibar national anthem played. The visiting princes seemed touched by the gesture, much to the crew's relief.

The inspection duly proceeded. With the aid of an interpreter (the princes spoke no English), the visiting party made clear its complete satisfaction with the Dreadnought and her crew. They were very impressed with the ship, very grateful for the warmth of their reception, very pleased to be able to report back home that all was well with the Royal Navy, etc. Captain Richmond was suitably chuffed, and bid them a happy farewell as they departed.

The problem with all of this is that there were no Abyssinian princes. Herbert Cholomondeley did not exist, and certainly did not work for the Foreign Office. The "interpreter" was not interpreting anything, and the visitors were speaking gibberish made up on the spot.

The visitors were in fact artfully disguised members of the Bloomsbury Group, a literary and artistic coterie that had at the time attained a somewhat notorious reputation in England. The ringleader of the hoax was Horace de Vere Cole (who never met a joke he'd turn down), but it involved a number of the leading lights of the Bloomsbury scene, such as Adrian Stephen, the painter Duncan Grant -- and a young Virginia Woolf. They had been made to look like "Abyssinians" by the accomplished theatrical designer and make-up artist William Clarkson.

The hoax quickly became public knowledge and the Navy was suitably chastened. The tricksters were never formally punished, as it was not apparent what law (if any) they had actually broken. It became a matter of national embarrassment that a group of uncredentialed people off the street could simply board and walk around the Navy's flagship with impunity -- this, too, during a time of heightened international tensions.

Security was tightened significantly after the hoax, thankfully, but all involved were keenly aware that it could have been far worse.

At some point in the mid-460s BC, the Athenians and their allies under the general Kimon annihilated a Persian fleet and army in a single day at the Eurymedon, crushing Persia's final attempt to take Greece by force. Despite its magnitude, this event is so poorly known that we're not even sure in which year it happened. Our most contemporary source, the historian Thucydides, says little more about it than what I just wrote here.

However, the later historian Diodoros of Sicily obliges us with a more fleshed-out version of the story. In his account (11.60-61), the Athenians first fought and captured the Persian fleet. Kimon, hoping to overcome the enemy army by surprise, then ordered his men to dress up in full Persian gear and man the captured ships. He waited until nightfall, and then made for the beach where the Persian army was encamped. Recognising the approaching triremes, the enemy thought their own fleet was coming to land, received the Athenians as friends. The Athenians promptly attacked the camp, scattered the panicked Persians, and killed one of their commanders, a nephew of Xerxes himself.

We can't tell where Diodoros got this tale from, and the whole thing may be fanciful fiction - but at least it has Greeks dressing up in trousers and tiaras, so there's that.

In Aalst, a small city in Belgium, people celebrate mardi gras in a rather weird fashion: men dress like women during three days of feasts before Ash Wednesday.

Historically, this dates back to the early 20th century, when the city was dominated by a very small upper class, which owned all the factories in the area. The majority of the people dwelled in poverty and were entirely dependant on those factories and the underpaid jobs there. (Look up "Daens" for a look into these horrible times)

Every year, the aristocracy would celebrate the start of Lent with a masqueraded ball, with magnificent costumes, masks, etc.

The poor of Aalst decided they wanted to have their own "bal masquee" and, since they couldn't afford costumes, simply used whatever clothes they found in their wives' closets.

This tradition survives to this day and is recognized by UNESCO!

So is Sibylla the first recorded case of a Scooby Doo villain, or is there a case of one further back?

Jannisaries of Ottoman Empire used to wear chef hats as their formal uniform. This is in fact, how their organisation works. ''Yeniçeri Ocağı'' which roughly translates to ''Janissary Hearth/Kitchen''. They also formed ''Brotherhood of Spoons'' among their brothers-in-arms and their ranks have kitchen inspirations too for example there is an officer rank of ''Soupmaster/Head of Soup'' in their organisation.

TL-DR: Janisarries did Kitchen Cosplay.