http://fguniverse0.tripod.com/pilot.htm states:
Ah, the famed pilot episode. Some people say it doesn't exist. They are dead wrong, but some people still say it. The pilot episode was created when fox gave good ol' Seth a small budget to create a short episode of Family Guy. He was able to create almost a full episode to their surprise and fox gave him the job. Many people don't know that the pilot episode is almost the exact same thing as 101 - Death Has A Shadow. Their are a few differences though:
a.. Many of the voices are different (due to the limited budget) b.. The animation is much rougher. MacFarlane had to draw late into the night for 6 months, give him a break. c.. Chris is much different - he's boring and just isn't as funny d.. Some of the characters like Cleveland and Quagmire aren't there. e.. Different music...a bunch of other things; no money = no fun :( READ THIS AGAIN - The pilot episode is almost the exact same thing as 101 - Death Has A Shadow.