Leonardo

Leonardo is a mutant turtle and one of the main characters of the series. The color of his mask is blue and his weapons of choice are katanas. He was voiced by Jason Biggs from Season 1 to most Season 2 episodes, Dominic Catrambone in various Season 2 episodes (including the video game), and is now voiced by Seth Green in Season 3.

Physical appearance
He is an antropomorphic turtle with a blue mask, weilds katanas, some belts, has dark green skin, and has some scratches on the front of his shell.

Personality
Leo is a brave, caring and responsible turtle. He was chosen to be the leader (because he asked Splinter). Like his brothers, he enjoys eating pizza.

Early life
When Splinter was still a human, he moved to New York City to get a new life. He went to a pet store and adopted four baby turtles. While he was walking, a strange man bumped into him. Something felt "off" about that man. He proceeds to follow to see what's going. He finds the strange man with other identicals in an alley. The men spotted him when he accidentally stepped on a rat. The men spoke with a strange, robotic tone as they proceed to attack him. Splinter managed to fight them off, but the canister of mutagen they were holding falls on him, making him drop his turtles. This caused Splinter to transform into a mutant rat, and his turtles become mutants. Knowing that the humans wouldn't accept him in his current form, he moved to the sewers with his turtles. Splinter then trained them as ninjas. He found a book of sculptors and painters of the Italian Renaissance, in which he named all of the turtles after the Renaissance artists. And he rasied them as his sons.

Raphael
When leading the team, Raph sometimes criticizes him on doing something better. Leo is always frustrated of his negative attitude. However, they're still brothers and they help each other.

Karai
When he first met her, he seems to have a crush on her. One time, she tossed a knife at him so he can release himself from Snakeweed's grip. Karai sometimes wants him to do things wrong, which he refuses. Leo also believed that Karai is good until it is revealed she betrayed him.

In Wormquake! (aka The Manhattan Project), he told Karai that Splinter is her true father, but she thinks he was lying. Later on in The Wrath of Tiger Claw, Karai tricked him into believing Splinter is her father so she can track Tiger Claw. However, when Karai finally learned the truth, she reveals that she was lying to the Turtles. When she was captured, Leo was sad, but Raph never wanted to trust her.

Trivia

 * Leonardo was named after Leonardo Da Vinci
 * He seems to have a crush on Karai.
 * His favorite TV show is called Space Heroes.
 * In TCRI, he learns how to speak like the Kraang.
 * Leo's greatest fear is losing his team.
 * In Season 3, his voice changed due to the damage he sustained from his throat.