The Moomins (1978)

S1E41 The Night on the Tree

Dad is fed up with drifting on the water, so he secures the theater to a tree. Moomin and Snorkmaiden curl up and doze off in the branches. However, during the night, Emma unties the rope, and the theater floats away. The following morning, the Moomintroll children embark on their own adventure and eventually arrive at solid ground.