Castor (formerly known as Zuse) is a program in Tron: Legacy. He is a flamboyant and vivacious program that owns and operates the End of Line Club, a nightclub located on top of the tallest tower in Tron City. He is portrayed by Michael Sheen.
- For the role, Michael Sheen had to wear light blue contacts.
- The symbol on his forehead may be a modification of the Ubuntu logo. This, coupled with the name Castor is most likely a reference to the Castor Project, and in particular the "castor" ubuntu package. Compare with Suse and Opensuse, a Linux distribution.
- The name Zuse is possibly either a reference to the Zuse Z3, which was one of the first fully functional programmable computers, or its inventor: Konrad Zuse.