Fact: Creator of Family Guy, Seth MacFarlane originally envisioned the show as a short clip for MADTV in 1995, which might have sparked the actually series.
The original concept for Family Guy was a short segment of clips that would appear on various episodes on MADTV. However, the plan fell through and the series ended up being created. Many of the originally planned voice actors from MADTV Debra Wilson, Phil LaMarr, Alex Borstein, James Wood and Nicole Sullivan all appear in the series. But the only one to freely remain a full time cast member on the show is Alex Borstein who plays Lois Griffin.
The character of Peter Griffin is actually based on a real person. Seth McFarlane knew a security guard in college who had a similar persona to Peter’s.
The long running gag about what Meg’s full name was eventually revealed online. While thought to be short for Megan her name has been confirmed to be Megatron Griffin after Peter switched out her birth certificate (what a soundboard). All the scenes for Meg and her abuse was the result of an all-male writing staff not know what to do with a teenage female character that would seem authentic.
Brian is based off of Seth MacFarlane. So much so that Seth doesn’t alter his voice at all and all of his views on life, religion and beyond are shared with Brian.