And lets not forget Dirk Gently's Holistic Detective Agency, which recycled the character of Professor Chronitis.
Oh yes, of course, I did forget. It did more than that, in fact: much of its storyline was taken directly from both "Shada" and "City of Death" (also by Adams).
Thanks for the clarification. I thought it did, but it's been so long since I read it that I couldn't really remember, and I didn't want to risk claiming it reused more than that. I just remembered recognizing the character and thinking "Wait a minute... this is Shada!"
I certainly don't blame Douglas Adams; at the time none of the other "completions" had been done, and why not retool a story that hadn't gotten to see the light of day?
He did the same thing with Life, the Universe, and Everything
... it was also based off of an abandoned Doctor Who story outline he wrote, where the Doctor encounters the Krikkitmen. I remember reading an interview with him discussing it (I suspect it was in Neil Gaiman's Don't Panic
) where he said the biggest problem was that where the Doctor would want to rush in and solve the problem, Arthur would rather let someone else worry about it and try to find a good cup of tea and Zaphod would rather find a good party!