I is for...

IAN Bancroft
Bancroft was a senior member of the Watchers organisation who was killed by fellow Watcher Rita Luce when he suspected that her relationship with her charge, Immortal Michael Christian, wasn't purely observational. Bancroft had been watching May-Ling Shien, an old flame of Duncan's (who wasn't?), but she was killed by Christian after a tip-off from Luce (C12, They Also Serve).

IMMORTAL
Immortals, like Duncan Macleod, Hugh Fitzcairn and Xavier St Cloud cannot be killed unless they are beheaded. The Immortal can be 'killed' temporarily, but will revive and heal. Any wounds (aside from amputations) and scars are also healed, and they are immune to disease. Being sterile, Immortals have little need for birth control and so tend to put themselves about a bit. Well, Duncan does (and Fitz come to think of it) anyway.

J is for...

JAPAN
Macleod was shipwrecked here in 1778. His rescuer, Hideo Koto, was forced to commit hara-kiri as a result of harbouring an outsider in the isolationist empire. Still, Duncan did get his katana out of it, and has carried Koto's sword as his own ever since (C1, 'The Samurai').

Charlie JOHNSON
Ex-lover of Amanda's, who calls on her and Nick for help when he becomes convinced his son was killed by the government for trying to expose a conspiracy involving attempting to manipulate the world's population levels (more's the pity) - R5, 'So Shall Ye Reap'.