"He spread this rumor that I was f-cked by about 12 sailors," the British rock star tells Andy Cohen and Cyndi Lauper.
"I did email her and say, 'What? Again, dear?' And I didn't hear anything back," he joked. "But talking about the retirement, I've never spoken about retirement, and if I do retire, I won't make an announcement. I'll just fade away."
Stewart added that John making a "big deal" of his retirement "stinks of selling tickets." And although Cyndi Lauper -- who was sitting beside Stewart -- tried to argue that a farewell tour was not such a bad idea, Stewart maintained that it felt "dishonest."
But the rock star did cut his buddy some slack for recently storming out of a Las Vegas show after a fan charged the stage and proceeded to harassed him.
"I sort of understand," he said. "I can see why he was pissed off with it."
Cohen then asked Stewart if he was now able to laugh off the stomach-pump rumors that plagued him years ago. Lauper had never heard of said rumors, so Stewart proceeded to explain.
"There was a publicist of mine that was gay and I had to fire him," he began. "He was getting really mean. And he spread this rumor that I was f-cked by about 12 sailors and I had to be taken to a San Francisco hospital and have my tummy pumped to take all the semen out."
"12!" he added. "That's a lot of-- (insert inappropriate hand gesture here)."