Springfield's four-fingered folks just zipped by the modern Stone Age family as TV's longest-running prime-time cartoon. Last Sunday's show was the 167th episode of The Simpsons, which first aired as a series in 1990. (The Flintstones ran 166 original episodes from 1960 to 1966.) Says creator Matt Groening, who in just 15 minutes dreamed up the idea for The Simpsons: "I can't believe we've been annoying people for this long."