The pilot featured only a small cast of characters, and following its commission into a series there was a need for additional characters. Many were picked for their roles in previous series; Mark Wing-Davey had played a character in "The Glittering Prizes" "who took advantage of people and was very trendy", making him suitable for the role of Zaphod, according to Adams. Richard Vernon, noted for his portrayal of "grandfatherly types", was chosen as Slartibartfast. Other characters included Susan Sheridan as Trillian and Stephen Moore as Marvin.