Lambert is the foster son of Mrs. Sheep, having been accidentally brought to a meadow as a cub alongside some lambs by a stork. He is initially very cowardly until his adoptive mother is put in danger, whereupon he displays amazing courage.
Lambert is brought to a meadow on accident by a stork. Upon seeing the lambs with their new mothers, he chooses Mrs. Sheep to be his mother, much to her joy. The stork realizes his mistake almost immediately, and attempts to take the lion cub to South Africa where he belongs, but is quickly stopped via a headbutt from Mrs. Sheep.
Lambert attempts to play with the other lambs, but he is teased for his decidedly un-sheeplike appearance and habits. They make him bleat but he only meows due to being a cub. This culminates in a headbutting contest which Lambert loses badly, leading to his cowardly habits.
By fall, Lambert has become an adult lion under Mrs. Sheep's care, but still remains the butt of the jokes of the now-grown sheep. This changes one night when a wolf attacks Mrs. Sheep, and when he threatens Mrs. Sheep, Lambert is petrified and assumes the flock will help, but they run and hide. Hearing his mother bleat for help, Lambert snaps and becomes a raging lion, roaring at the wolf and headbutting him off the cliff he stands on. Due to his courage, Lambert is held in high regard by the sheep who had previously teased him.
Lambert (unnamed) lives in Africa, where he roars to scare off all the other animals. He then gets sent off to the city, where he causes more chaos. He later arrives in a zoo and wreaks even more havoc with his roaring, until he is eventually taken back to Africa.