Nancy Marchand (The Sopranos)
The Sopranos third season was to feature Nancy Marchand in a major role that involved Tony (played by James Gandolfini) attempting to prevent Marchand’s character from testifying in court. It was quite a significant arc for both characters and involved a few important plot twists. Alas, with Nancy Marchand’s death, the producers had to re-write the whole season and shift the plot’s focus on Tony’s family and their ordeals. With the help of some CGI, Livia (Nancy Marchand) was brought one last time for a final scene in season three.
Andy Whitfield (Spartacus)
Starz Entertainment was burdened with an impossible task to re-cast the title character of the popular show Spartacus after Andy Whitfield was diagnosed with non-Hodgkin Lymphoma. Various actors portrayed his character in Spartacus: Gods of the Arena, while Andy Whitfield was undergoing treatment, but when he couldn’t return to film the second season of the show, he was replaced by Liam McIntyre. Whitfield was only 39 when he passed away on Sept. 11, 2011.