Short answers, pulled from the story.
The Japanese government announced a loan of giant pandas to Ueno Zoo in September 1972. This diplomatic gesture from China sparked an immediate cultural craze across the nation.
Isao Takahata and Hayao Miyazaki left Toei Animation studio in 1971. They joined fellow animator Yasuo Otsuka at A Productions to pursue new creative goals.
Astrid Lindgren gave a flat refusal for adaptation rights when Takahata and Miyazaki traveled to Sweden to seek permission. The rejection forced the trio to rethink their entire project direction and transform discarded concepts into the story of Panda Kopanda.
A nasty storm breaks overnight and floods most land around Mimiko's hometown while the circus train carrying all animals gets stuck in the middle of nowhere. Mimiko and her family free the animals but cause the train to start moving toward the mayor's house before PapaPanda stops it from colliding with the building.
Animator Yoshifumi Kondo served as key animator on both panda films after working extensively on Lupin III Part I TV series. His contributions helped establish him as a vital figure in future Takahata and Miyazaki productions including Anne of Green Gables and Grave of the Fireflies.