Two Ghibli created shorts about the happenings in a fictional animation studio, presumably based to some extent on their own.
Animation Seisaku Shinkou Kuromi-chan
Mangirl!
Panda Kopanda
Pinky Wakuwaku Tabi Stroll
Ghibli ga Ippai Special Short Short
Kaze no Tani no Nausicaä
Kemushi no Boro
Takara-sagashi
Sanzoku no Musume Ronja
Mizugumo Monmon
Yuki no Taiyou Pilot
Hoshi wo Katta Hi
Dore Dore no Uta
Ged Senki