On television, the animated series "Futurama" makes frequent references to "Star Trek" and parodies some of its better known plot elements on a regular basis, including the character Zapp Brannigan who is based on a combination of Captain Kirk and William Shatner, and cast members of the original series have taken part in one episode. Prominent examples in other television series include multiple episodes of "The Simpsons" and "Family Guy". The children's series "The Backyardigans" has an episode titled "Garbage Trek" that is an homage to the original series. Joss Whedon has cited "Star Trek" as being the father of his cult series "Firefly" and its film "Serenity" (2005).