I read that Count Petofi was based on Count St. Germaine, a medieval alchemist who cllaimed to have attained the secret of immortality. He does have an appearance in Charles Delaware Troll's continuation of the series.
one of my personal all-time favorite moments on DS--that shot of the DS skeleton tarted up in Wanda Paisley's tea-gown, wig, and big feathery aigrette