A while back, there was a traveling group of performers. All of them had reasonable skills, enough to wow the farmers they entertained. Things continued on just fine until one fateful day, when passing through a small community on the edge of the forest, one of the performers, Jonathan the magician, was bitten by a werewolf.
It didn’t take very long for the rest of the troupe to find out, and while they were concerned for him they were more concerned about themselves. They gently explained to him that in his present state he was no longer welcome to travel with them, due to the danger he presented. Setting out on his own, Jonathan eked out a living by performing his tricks in large cities, places where he could hide when the transformation took him.
He continued like this for months, scraping a living as best he could, until one day competition arrived. A burly man performing shocking feats of strength was pulling away the bystanders, who had started to grow bored of Jonathan’s act. During the next full moon, when Jonathan had decided to head for the next city in his wolf form, he saw what he could have sworn to be a bear rummaging through a pile of refuse.
Two things struck him as odd about this: one, that there weren’t any bears for a week’s travel from the city, and two, that this particular bear had odd markings that were very similar to those of the strongman.
Deciding to postpone his trip to the next city, Jonathan confronted the strongman the next day. The man, Sebastius, denied it as silly and proceeded to mock Jonathan. More sure of himself than before, Jonathan waited for the next full moon and used his senses to track down the bear. Upon finding it, he proceeded to follow it for the rest of the night, until the moon went down. Sure enough, it was Sebastius. Immediately confronting the big man, Jonathan was about to let him know of his plans to expose him when an realization struck him: there were more like him! Changing the course of the conversation mid-topic, he told Sebastius that they could seek out others like themselves, that the best place to hide is in plain sight, and where better than a stage? After convincing the big man, the two set out to find more like them.
Slowly, they accumulated more people. It turned out that a particular forest that a number of small towns border was actually home to a number of the werebeasts, who every now and then assaulted one of the performing troupes that so often came near.
Soon, they had assembled a rather exotic little group: twins, Elves, a Dwarf, an Orc and a Dark Elf amongst them. Moving as a group, they became rather successful, as many would pay just to be able to see a Dark Elf or an Orc without fear of immediate and disfiguring injury. The true turning point for the group though, was the discovery of an odd potion that, when ingested, triggered transformation in werebeasts. Although intended to help root the creatures out, it allowed the performers to do the greatest "transformation" tricks that anyone had ever seen.
Now, the recently christened Silvermoon Carnival has gained a reputation as having reasonable prices, good kettle corn and spectacular performances.
For a darker take on this, it’s possible that in his efforts to recruit more Lycanthropes to his group, Jonathan has gone so far as to purposefully infect talented performers. Such new members would likely have trouble controlling themselves in their new forms, and for the first few months it would be not too uncommon to hear that a couple of people went missing when the carnival was near.