Brothers & Sisters

Unusually for a show that turned out to be a critical and commercial hit, in the weeks before the first episode aired, this show went through several cast and crew changes. The Walker family matriarch, Iva, played by Betty Buckley in the original pilot, was re-cast with Sally Field, and renamed Nora. Walker brother Bryan, played by Jonathan LaPaglia, was re-cast with Matthew Rhys, renamed Kevin, and given a new backstory (instead of Bryan being an ex-husband and father, who was newly out of the closet, Kevin was a never-married lawyer, who was more comfortable with his homosexuality). Marti Noxon was replaced as the showrunner by Greg Berlanti, because of creative differences.

In the final season, there is a story line about Sarah's biological father and blood types. Both William Walker and Nick Brody have type B blood, and it was revealed in a previous season that Nora has type O blood. Sarah's blood type is said to be AB, but this is impossible. For a child to have type AB blood, there must be some combination of A and B. Either one parent is A and the other is B, or one parent is AB and the other has any other type. If Nora has O and both fathers have B, Sarah must have either type O or B blood.