Black Jack: Dr. Pinoco's Adventure(2005)

Black Jack: Dr. Pinoko no Mori no Bouken

Dr. Black Jack forgot his doctor's bag, and his assistant (plus self-claimed "wife") Pinoko rushed to deliver the bag but found herself lost in the forest. Guided by a butterfly, she found that many animals in the forest are sick or injured, and Pinoko used her knowledge to help those animals.

(Source: Anime News Network)