Disney's Adventures of the Gummi Bears (1985)

S3E12 The Knights of Gummadoon

As the knights of Gummadoon's castle materializes, Cavin finds himself locked away, accused of being a spy. The Gummies must act fast—they have until sunset to save him, since the castle only shows up once every century. However, they face a significant challenge: Duke Igthorn has his own plans to seize control of the castle for himself.