Mrs. Sheep is Lambert's foster mother. She immediately took him in when a stork mistakenly delivered a lion cub to her. However, she decides to adopt him anyway and headbutts the stork when he attempts to take the baby lion from her. The stork then leaves in a huff and lets Mrs. Sheep keep the lion cub.
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.
Mrs. Sheep attempts to get Lambert to play with the other lambs, but he is teased for his decidedly un-sheeplike appearance and habits. 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 the flock, and when he threatens Mrs. Sheep, Lambert is petrified and assumes the flock will help, but they run and hide. Hearing his mother cry 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 praised by his adoptive mother and held in high regard by the sheep who had previously teased him.