The Battlestar Galactica science fiction franchise, which began as a 1978 TV series, was "reimagined" in 2003 into a TV miniseries. The miniseries served as a backdoor pilot for a 2004 TV series. Three seasons of the TV series have been completed and aired, along with a two-part prequel Battlestar Galactica: Razor, which also constitutes a preamble to the fourth season. The fourth season, consisting of 20 additional episodes (excluding Razor which takes up an additional 2 "slots"), began airing on 4 April 2008, and constitutes the finale for the series. This new Battlestar Galactica is described as reimagined not only to avoid the negative connotations associated with the term remake, but also because it marked an entirely new direction for the franchise, while still based on the original premise; it is analogous to a reboot in comic books. The new Battlestar Galactica departs from the original in several ways. In terms of style and storytelling, it rejects the traditional televised science fiction styles of Star Trek (after which the original Battlestar Galactica series was conceived) in favor of what executive producer Ronald D. Moore calls "naturalistic science fiction." The new series emphasizes character drama in an edgy survivalist setting and has many of the characteristics of military science fiction, shedding the light-hearted action/adventure style of the original show. Among plot differences, the key characters of Starbuck and Boomer have been recast as female roles. The Cylons are the creation of man and a new breed of Cylon models now imitate humanoid appearance down to the cellular level.