Short answers, pulled from the story.
Isao Takahata, Hayao Miyazaki, and Yoichi Kotabe created the 1974 Japanese animated TV series Heidi Girl of the Alps. They began production in 1973 after taking a research trip to Switzerland to ensure authenticity.
The production team visited Switzerland in 1973 before the series began. They traveled to Maienfeld and stayed at the Heidialp hut to study the real-life setting of Johanna Spyri's novel.
The character designer Yoichi Kotabe changed Heidi's hairstyle after a Swiss librarian corrected him. The librarian explained that a five-year-old mountain girl would not be able to tie her hair in two pigtails.
Heidi suffered from a serious case of homesickness that manifested as sleepwalking when she was sent to Frankfurt. The doctor diagnosed her condition and persuaded Mr. Sesemann to send her back to the Alps before she died of her condition.
Clara Sesemann recovered from her paralysis after visiting the Swiss Alps with Heidi and Peter. The doctor determined the terrain was appropriate for her, and the children worked on her physical therapy until she could walk without assistance.