PK changed its name because there turned out to be an older band from the Netherlands that was already called PK. They apparently didn't bother to Google their new name before choosing it, because there is also an Australian band called Night Riot. I don't know if the added s will be enough to keep them out of trouble.
The name PK reminded me of P.K. gum, a Wrigley brand named for founder Phillip K. Wrigley. It was a pellet gum, like Chiclets, rather than the usual Wrigley style stick gum, but it came in a standard stick-gum shaped pack, stacked like Pez candy. I don't recall seeing the stuff since I was a kid, and I don't think it's been available in the American market for ages, but Google tells me they still have it in Australia, where it has a page on the Wrigley web site. They've even added a licorice flavored variety along with the original peppermint.If I ever go to Australia I'll buy some. I might catch a performance by Night Riot, too.