Two important cast changes were made for the TV version. David Dixon replaced Geoffrey McGivern as Ford, and Sandra Dickinson replaced Susan Sheridan as Trillian. The changes were made because McGivern did not suit the role visually, and Sheridan was unavailable at the time. Another new cast member was Michael Cule, who appears as the Vogon Guard in episode two. Cule had first appeared in one of the "Hitchhiker's" stage adaptations, performing no fewer than twelve roles. He reprised the Vogon Guard part in the 1992 "Making of the Hitchhiker's Guide to the Galaxy" TV documentary, voiced the Babel fish, appeared in the 1994 photo illustrated edition of the book (as Prosser), and returned a third time as a Vogon Guard for the BBC Radio 4 "Quandary Phase."