These codes are courtesy of Father Bronze - I have lifted them from his 'hidden NPCs' thread (which I hadn't seen when I wrote my last reply to this post):
TTXAN - Xan
GITH03 - Githyanki Anti-Paladin (complete with Unholy Reaver sword)
BIFF - Biff the understudy
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Time is an illusion. Lunchtime doubly so.