In the 1980s series, Jeffrey Tambor did several voices such as Hard Rock and Dr. Bradshaw in "Deadly Junket", and Dr. Zin in the two TV movies.
Scott Menville voiced Jonny in the '80s series, while Rob Paulsen played Hadji.
What Could Have Been: An article in Television Chronicles stated that Hanna-Barbera had planned at least 39 episodes for the '80s run of Jonny Quest. The dismal ratings and negative reaction played a part in the series' cancellation after episode 13.
Jessie Bradshaw was originally conceived as a character that would appear in a few episodes of the '80s series as a female counterpart to Jonny. When it came down to the actual episodes that were finished, she only appeared in "Deadly Junket". The misconception that she was a regular new addition comes from the writer stating his original plan, as well as fans confusing her with the later Jessie Bannon incarnation.