Wayne Alexander, who played Sebastian, actually grew up in California's San Joaquin Valley. He was quite flattered when he learned that his upper class English accent in this episode was so good, audiences in England wholeheartedly accepted Sebastian as an actual Englishman.
Sebastian's line "Who are you?" was later one of the phrases featured in the opening sequence of Season Five.
Sebastian's quote about laying down one's life is derived from the New Testament's Gospel of John 15:13: "No greater love hath a man than he lay down his life for his friends."
This takes place from December 19 to December 20, 2259.
Asking "Who are you?" and not accepting any response was one of the standard tactics in 1970s California pop-psychology cults of the Erhard Seminar Training type.