When Harald Siepermann was working on Mr. Arrow in September 1998, the visual development stage of Treasure Planet was reaching its end. For the few remaining weeks, the directors Ron Clements and John Musker wanted Harald to work on the characters Dr. Doppler and Sarah, the mother of Jim Hawkins. Eventually Harald didn’t work on the character Sarah, but he spent some times creating visual development for Dr. Doppler.
In the script he’s described as nerdy and dog-like. Doppler was Jim Hawkin’s astronomer friend. Thanks to an inheritance, Doppler is the most wealthy of all the locals on the planet. But he is an eccentric recluse, overflowing with theoretical knowledge, yet nearly devoid of personal experience.
Although it was clear that the character would have dog-like features, it seems that Harald neglected that part in his designs. It is not really clear why, since Harald never elaborated much on his design approach for this character, despite that he described this for the other characters from Treasure Planet on his personal blog that he kept active for several years. Below is a series of his designs:
The final design for Doppler was created by Supervising Animator Sergio Pablos.
Since the visual development stage was reaching its end, the directors asked Harald to leave the character Doppler, and work for the remaining 15 days on the pirate Hands.