Christopher Lambert originally asked for just $50,000 to appear in the pilot, but one of the French investors protested it was too much money and had him written out. This made the German investors threaten to withdraw, so he was put back in. But he'd gotten annoyed by the situation so he refused and as a result he was eventually paid $500,000 for 3 days of work.
The series was originally planned to follow the film, with Connor MacLeod in the lead role, to be played by Adrian Paul. Paul, however, wanted the freedom to create his own characterization, and to avoid direct comparisons to Christopher Lambert, so the writers agreed to create a new character.
The character 'Duncan MacLeod' was ranked #11 in TV Guide's list of the "25 Greatest Sci-Fi Legends" (1 August 2004 issue).
The character of "Matthew McCormick," the immortal who works as a federal agent tracking serial killers, was created specifically for actor Eric McCormack. The producers even considered giving him his own Highlander spin-off series, in which McCormick would travel the country where ever there was a series of beheadings and "investigate" the crimes while simultaneously dispensing immortal justice.
The season five finale, Archangel (1997), was originally shot with a cliffhanger ending set 20 years in the future, when MacLeod is finally prepared to defeat Ahriman. The sixth season was planned to happen in the future, but was deemed too dark early on and was finally scrapped when the budget was sliced.