Lenny is the deuteragonist of Shark Tale. He is the second-born son of Don Lino, and younger brother of Frankie. He is a friendly and outgoing vegetarian great white shark. Lenny isn't an aggressive meat-eating carnivore like his older brother or father, but a vegetarian. Lenny has a heart of gold and he quickly becomes close friends with Oscar. Together, he and Oscar faked Lenny's defeat at the hands of the "Sharkslayer", and after that, Lenny disguised himself as "Sebastian the Whale Washin' Dolphin". He later helped Oscar save Angie, during which Lino grew to think that Lenny had turned against the sharks. Eventually, Lenny made up with his father after Oscar admitted that an anchor had killed his brother Frankie.
In the first scene, the worm though the shadow of the shark was going to get him, but the shark revealed to be Don Lino's youngest son and Frankie's younger brother: Lenny. The worm looked at Lenny and it fainted and Lenny said, "Oh! Little buddy did I scare ya? I'm sorry."
Unlike most sharks, Lenny is friendly, compassionate, and a vegetarian. He deeply respected all life and refused to kill fish or anything else, which exasperated his Lino and Frankie. Even though his relationship with his family was strained, Lenny was devastated when Frankie was killed by an anchor. He loved his father, but was afraid of disappointing him, so he decided to run away and never return.
However, Lenny did return in order to help Oscar save Angie, which made Lino think he was working with the enemy. Eventually, Lenny and his father reconnected after Oscar revealed that Frankie's death had been an accident. Lenny quickly became close friends with Oscar and also took a liking to Angie. He has also shown to be able to come up with good ideas, such as when he came up with the idea of faking a fight with Oscar to make it look like he met his demise.