Lambert is the foster son of Mrs. Sheep, having been accidentally brought to a meadow alongside some lambs by a stork. He is initially very cowardly until his adoptive mother is put into 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 Lambert 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. 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 held in high regard by the sheep who had previously teased him.
- Ironically, Lambert's color scheme resembles that of Scar's and/or Kovu's.
- The lion that appears in the Disney cartoon short Social Lion bears a striking resemblance to Lambert, even having the same only line of dialogue, "Mama?!" This is due to much animation from Lambert the Lion being reused for Social Lion.