The voice of ghost king in this film is given by famous director Satyajit Roy himself.
The Raja of Amloki quizzes Goopy about notes of the scale. The Indian do-re-mi scale is sa re ga ma pa dha ni. The raja asks Goopy the third and sixth notes of the scale, and he answers ga and dha. The raja says "That's what you are!" because the two syllables make "gadha": the Bengali word for donkey.
Santosh Dutta played double role in the movie