Inappropriate Content Hallucination, as defined by a recent study conducted by researchers at the Rochester Institute of Technology, is when artificial intelligence systems insert dirty words into the subtitles of videos meant for kids.
From their article:
Over the last few years, YouTube Kids has emerged as one of the highly competitive alternatives to television for children's entertainment. Consequently, YouTube Kids' content should receive an additional level of scrutiny to ensure children's safety. While research on detecting offensive or inappropriate content for kids is gaining momentum, little or no current work exists that investigates to what extent AI applications can (accidentally) introduce content that is inappropriate for kids.
In this paper, we present a novel (and troubling) finding that well-known automatic speech recognition (ASR) systems may produce text content highly inappropriate for kids while transcribing YouTube Kids' videos. We dub this phenomenon as inappropriate content hallucination. Our analyses suggest that such hallucinations are far from occasional, and the ASR systems often produce them with high confidence.

More info:
Indian Express
According to legend, a bored weatherman stationed in the far north of Canada during the 1950s used a bulldozer to move earth and rocks to spell out a massive, four-letter expletive that was visible to planes passing overhead.
Is there any truth to the legend?
Well, the story traces back to some correspondence from
anthropologist Edmund Carpenter that was printed in
The Realist magazine in November 1964. Carpenter had lived for years in the Canadian Arctic. So he was a knowledgeable source of info about the region.
However, if the expletive cairn does exist, then, to date, no one has been able to locate it.
More info:
Straight Dope message board

The Realist - Nov 1964
Right in the middle of charming little St. Croix Falls, Wisconsin (population 2000), Geoff Gorres and his business partners opened a gun store. Their choice of name: F-Bomb Ordnance.
Local residents aren't too happy about it, thinking it lowers the standards of the community to have the f-bomb "displayed prominently" on Main Street.
In response to the controversy, the owner says he may be willing to consider other options for signage, but he's definitely keeping the f-bomb name. More info:
CBS (WCCO);
The Sun.
Caution: many, many swears.