Three from Buttermilk Village

Three from Prostokvashino Russian , tr. Troye iz Prostokvashino is a 1978 Soviet animated film based on the childrens book Uncle Fedya, His Dog, and His Cat by Eduard Uspensky. The film has two sequels, Vacations in Prostokvashino 1980 and Winter in Prostokvashino 1984.

Uncle Fyodors parents became very agitated at the loss of their son, and even put out a missing persons notice in the paper Such a notice couldnt pass the nose of the extremely curious mail carrier Pechkin, who right then and there declared his hopes to earn a reward for the boys safe return a new bicycle.

Source: Wikipedia