Disclaimer: Percy Jackson and the Olympians belongs to Rick Riordan. (Or Percy Jackson does, anyway. Last time I checked, the Olympians were public domain.)
"Okay, can you explain this to me?" said Loretta Hanft as she walked back to Cabin 4 with her half-brother, Jonathan Mellen. "Why does our cabin always meet with disaster during the chariot races?"
"Well," said Jonathan thoughtfully, as he limped along on a leg that had been crushed between their chariot and that of the Dionysus cabin, "maybe because we're the cabin of plant life, which wouldn't tend to make us comfortable around things that move of their own volition…"
"Oh, come on," said Loretta. "Husbandry and horses have gone together ever since the wheeled plow was invented. Maybe we don't have the natural gifts of someone like Jackson, but we ought to be able to handle a Pegasus – and we can; you saw the way Fatima dealt with our team just now. So why does something always go wrong?"
"Possibly," suggested a voice behind them, "because your mother is the patron goddess of mishap."
The two demigods turned around and stared at Mr. D, who was leaning against the Thalia pine with his usual self-satisfied expression. "Demeter is?"
"Mm-hmm."
"I thought that was Eris's job," Jonathan said.
"It was, for a while," said Mr. D. "Just the way the sun and moon were originally Helios's and Selene's respective headaches. But, as your neighbors in Cabin 5 will tell you, sooner or later the big fish always eat the littler fish, and the major goddesses snag the minor goddesses' patronages – all in the name of efficiency, of course."
"When did this happen?" Loretta demanded.
"In 1999," said Mr. D.
Loretta blinked. "1999?"
Mr. D nodded, a mischievous smile on his face. "That's when mortals started talking about Ceres of unfortunate events."