In "Predictable Smurfs," when Clumsy's boat returned to the dock where the regatta started and Clumsy asks Flighty why the other Smurfs are cheering them, Flighty's tail is white instead of blue.
In "Predictable Smurfs," Brainy's pod boat for the springtime regatta is made in the shape of a pumpkin. However, pumpkins were unknown in Europe until they were imported from the Americas in the 17th century and anything themed from them came latter on. The background of the Smurf cartoon series is the late Middle Ages (circa 14th-15th century), early for the appearance of pumpkins or anything themed from them (e.g. a boat in the shape of a pumpkin) in Europe.
In "Hefty's Rival," Wild uses a sunflower as a weapons to sling a bog-goblin into a pond to protect Hefty. However, sunflowers did not grow in Europe until they were imported from the Americas in the 16th century. The background of the Smurf cartoon series is the late Middle Ages (circa 14th-15th century), early for the appearance of sunflowers in Europe.