Joan Rivers

According to Joan Rivers, she has learned the power of Sarah Palin the hard way.

Rivers claims Fox News Channel canceled her Thursday morning appearance after TMZ reported that she called the former Alaska governor "stupid" and "a threat." Rivers, 77, tweeted about the incident Wednesday, writing, "Outcome: DON'T PISS OFF SARAH PALIN. She's apparently 'very powerful,' and is obviously still smarting from the end of her reality show."

Joan Rivers takes aim at OWN and Jersey Shore

Rivers also made light of the snub, threatening, "Wait till I REALLY shock them with Aretha Franklin is a bit chubby!"

Palin is a special correspondent for the Fox News Channel, which denied Rivers' claims, stating that her appearance has just been pushed back. "Due to the volume of news topics tomorrow morning and a full show, our booker mistakenly canceled Joan's appearance instead of re-scheduling her for Friday's show," Lauren Petterson, executive producer of FOX and Friends told Us Weekly. "We're in the process of booking her on an upcoming show."

Rivers is currently promoting her new WE TV reality series with daughter Melissa Rivers, Joan Knows Best?