On 25 March 2007, the series began its run on American television on the Discovery network, premiering on the Discovery Channel and Discovery HD Theater. There were a number of revisions to the original British programme. Actress and conservationist Sigourney Weaver was brought in to replace David Attenborough as narrator, as it was thought her familiarity to American audiences would attract more viewers. The Discovery programmes also used a slightly different script to the British original. The series was broadcast on Sundays in one 3-hour block followed by four 2-hour blocks. The "Planet Earth Diaries" segments were not shown immediately after each episode, but collectively in "Planet Earth: The Filmmakers' Story", a two-hour special which was broadcast after the series had finished its initial network run. Edited versions were later broadcast on The Science Channel, Animal Planet, and Planet Green.