They are also fans of Star Wars, Battlestar Galactica, and Doctor Who. James Earl Jones, Carrie Fisher and Mark Hamill make guest appearances. In the episode "The Ornithophobia Diffusion", when there is a delay in watching Star Wars on Blu-ray, Howard complains, "If we don't start soon, George Lucas is going to change it again" (referring to Lucas' controversial alterations to the films). In "The Hot Troll Deviation", Katee Sackhoff of Battlestar Galactica appeared as Howard's fantasy dream girl. The characters have different tastes in franchises, with Sheldon praising Firefly but disapproving of Leonard's enjoyment of Babylon 5. With regard to fantasy, the four make frequent references to The Lord of the Rings and Harry Potter novels and movies. Additionally, Howard can speak Sindarin, one of the two Elvish languages from The Lord of the Rings.