The FOX network's most successful series to date was a spin-off from The Tracey Ullman Show. Originally appearing on that series as a 1 minute filler, the executive producers of that series, James L. Brooks & Sam Simon decided that these characters could support a half hour series. So they did it and started the longest running animated series in primetime network television.

Part of this family's broad appeal has allowed them to make endorsements, such as the numerous commercials they've appeared in for Butterfinger candy bars.

FOX Broadcasting Schedule (All Times Eastern)
December 1989 - May 1990: Sunday 8:00-8:30
October 1990 - May 1994: Thursday 8:00-8:30
September 1994 - Present: Sunday 8:00-8:30

-taken from tv.com-