Ted Buchanan is the central antagonist of the Buffy episode "Ted" - he was one of the first threats that Buffy faced that was more science-fiction based than supernatural, yet he was also one of her more challenging opponents (especially considering he was a one-shot "monster of the week").
He was portrayed by the late John Ritter.
Ted Buchanan, often referred to simply as Ted, comes across as a sweet natured gentleman; as such he wins the heart of Joyce Summers, but not that of her daughter Buffy. Ted at first seems to act like a nice guy and tries to include Buffy into his new family as her potential new father. However, when Buffy begins to rebel, Ted starts to bully her and show a darker side. One night, after Buffy comes home from a failed patrol at Sunnydale Park, she finds Ted in her room with her diary and her Slayer stuff spread out on her desk. Believing that Buffy is delusional, Ted tells her to toe the line, or else he shows the diary to her mother and (in Ted’s words) Buffy will “spend (her) best dating years behind the wall of a mental institution.”
The situation climaxes when Ted begins to leave the room with Buffy’s diary, and the two engage in a seemingly fatal battle in which Buffy uses her Slayer strength on Ted and kills him.
Shocked at what she had done Buffy tried to reason both with herself and her mother but was overcome with guilt. However, the nightmare was not over for her or Joyce, as Ted Buchanan miraculously returned — very much alive.
It was then his true nature was revealed; Ted was actually a deadly robot. His creator (who was also named Ted) was a sickly inventor in the 1950s, whose wife left him. The robot that Ted made was intended to be “a better Ted” (possibly the man he thought his wife should have for a husband). The robot then kidnapped Ted’s wife and held her captive in his bunker until she died. Ted seemed to inherit his creator’s personality, and would befriend women before murdering them if they “misbehaved.”
Buffy fought Ted again to save herself and her mother from the murderous machine and managed to destroy Ted for good — thus ending his threat for good.