While Jay Carson (House of Cards) was originally lined up as showrunner, he was later replaced with Kerry Ehrin (Bates Motel, Parenthood), and the Wall Street Journal reported in September that the move was at least partly due to Apple's desire for more upbeat, family-friendly material. Last month, CNBC cited sources who said Apple was planning to make its streaming video service free, at least initially.

Along with Witherspoon, Aniston and now Carell, Apple has snagged a number of other high-profile names for its upcoming service, including Chris Evans, Octavia Spencer and Oprah.