Jay Leno returned to NBC's Tonight show Monday without a hint about the illness that caused him to cancel a show last week. He said that he came down with a fever after driving to the studio in one of his open-air Model T Fords. "Here at NBC we have an ODN, overly dramatic nurse," who insisted that he check himself in at nearby St. Joseph's Hospital. Neither he nor NBC described what might have caused his illness, although Leno, in an obvious reference to the swine flu, remarked in his monologue, "I ate a raw pig a friend brought back from Mexico. ... It was delicious." At another point in his monologue, he joked, "You see some pretty scary things in the hospital -- doctors in the next room were trying to revive NBC's primetime schedule."