Leonardo (TMNT, 2003 and 2018)

Leonardo in the 2003 TV series is more like Leonardo from the Mirage comics than the 1987 TV series and first three films. He is more well-balanced and serious than in the 1987 TV series and first three films. Like the Mirage comics and the film penology, Leo and Raphael have disagreements constantly, particularly in the City at War trilogy.

Physical Appearance
Leonardo appears to be a normal, healthy teenage mutant turtle. He is muscular and stocky like his brothers. His skin tone is forest green and he wears a blue ninja bandana. As of the season three finale, part of his shell by his left shoulder was broken off during the final fight with the Shredder, after Karai stabbed him in the shoulder.

Personality
Leonardo is the leader, whose key attributes consist of honor, sensitivity, patience, and encouragement. He is the most "spiritual" of the four brothers. Despite being a teenager, he acts kind of like a grown-up due to all his seriousness, but can still have fun with his brothers.

Of the brothers, he has the closest bond with Splinter, often going to him for help and attempting to follow his orders to a T (at least when his brothers aren't out causing trouble, forcing him to go along with their antics). While responsible, Leo can still be sucked into trouble by his brothers out of his own curiosity or his sense of duty to keep an eye on them.

Leo has a strong sense of honor and ethics, along with being a dedicated follower of the Bushidō code. Episodes that deal with the Shredder and honor usually also focus on Leonardo. He is also often the Turtle who "saves the day" (in fact, Leonardo is the turtle who decapitates the Shredder early on in the series—of course, before they are aware that Shredder is in fact an evil Utrom by the name of Ch'rell who doesn't have a neck, let alone a distinct head).

Why He Rocks

 * 1) He is a very mature turtle and proves himself to be a great leader and second only to Raphael, he’s probably the more serious and confident one of the Turtles.
 * 2) If anything, He is the most mature and responsible of the four brothers, and takes honor and responsibility as his priority.
 * 3) He is always an honorable leader throughout the shows 7 season run.
 * 4) He always takes responsibility for whatever problem occurs and will take the blame for what others do.
 * 5) He is well animated and looks awesome, it shows the effort that the creators put and is completely familiar of his Mirage Comic Design looks like the Mirage Turtles from the Comics.
 * 6) His voice acting is very talented, considering his voice actor also voiced Dean Venture (Michael Sinterniklaas). Season 4 was his best season he voiced Leo as he puts so much effort and especially when he was suffering Depression, Sinterniklaas does a good job especially making an intimidating voice.
 * 7) Whenever he battles the Shredder or the Foot Clan, his skills are always enjoyable as he has awesome skills using katanas showing how he trained for a long time.
 * 8) He’s also usually the “voice-of-reason” of the group as although Donatello is smarter, Leo is more of a reasonable person and will question his brothers decisions. He manages to be smarter in some ways such as Martial Arts due to the fact that he loves to learn more and more about it.
 * 9) He spawned an Internet Meme as the Tired Turtle. There is the meme where He looks dead inside.
 * 10) He saw a lot of character development as the series progressed, especially around Season 3-4 where we see is rougher and crueler side. He manages to get stronger as the series progressed, his wise self notably improved and so did his chemistry with his brothers.
 * 11) He is a very sympathetic character and truly cares a lot for his brothers, and father. As well as April and Casey.
 * 12) *He's very sympathetic and tragic when his badly beaten and nearly killed by Shredder and his foot soldiers after showing loads of persistent in, "The Shredder Strikes Back" parts 1 and 2.
 * 13) *The first half of Season 4 showed his rougher side in a fantastic way as we see how damaged and traumatized he is, following his fight with the Utrom Shredder and nearly being killed. His redemption is fantastic as he really goes to show how much he wants to redeem himself.
 * 14) His battles with the Shredder, especially in Season 1, are always entertaining considering that he is a trained ninja in the art of Ninjitsu.
 * 15) Leonardo has shown himself to be a very wise character with a lot of good tales, particularly, his tale on Hamato Yoshi.
 * 16) Although the other turtles feel as if Karai really does show no mercy for the turtles, Leo does show as if there is something good out of Karai and how she is better than her "father" (the Utrom Shredder) and how she can redeem herself from being evil.
 * 17) He has shown to have a great, strong and healthy relationship with his brothers, specifically Raphael and Master Splinter. Likewise, he has a wonderful relationship with Donatello and even Michelangelo, despite the fact that he may irritate him.
 * 18) He puts anyone loyal to him first, he always decides to think more about others rather than thinking for himself. This is presented in Enter the Dragons as he was at his best.
 * 19) Even when the show went downhill in quality, he was never flanderized and kept all of his charm as a leader and remained one of the most likable characters on the show and he is still a fan-favorite of the franchise.
 * 20) He is a fan-favorite of the show in general since his character has been praised by fans and critics for being the most faithful version of Leonardo and the best resembling to the comic books in general. Some even consider him the best version of his character in general.

Bad Qualities

 * 1) He became a jerk in Season 4, though he did suffer from PTSD (Post Traumatic Sleep Disorder, and he did redeem himself).
 * 2) Sometimes, he can show that he does not want to accept loss and brings himself down if he ever disappoints anyone.
 * 3) "The Shredder Strikes Back (Part 1)" showed how naive he can get as a character and how he was quick to jump to conclusions when he thought Oroku Saki could be a good guy, even though he was nearly being manipulated. Thankfully, Splinter showed him how Saki was actually evil and wanted world domination, helping Leo and his brothers to victory in their first battle.

Reception
The characterization and portrayal of Leonardo, alongside Michael Sinterniklaas providing an amazing performance would result in critical-acclaim from several critics and fans who praised the 2003 version of Leonardo for bringing a mature, calmer approach to the iconic cartoon character. His animated design also received strong reception for bringing a good resemblance to the comic books. In general, several have cited him as the best written version of Leonardo, alongside his 2012 counterpart.

Trivia

 * Like his brothers, Leo is a practitioner of Chi Gong, as shown in Turtles in Space - Part 3: The Big House.
 * In the season 3 finale episode, he was stabbed in the shoulder. In early season 4, when his bandages were removed, it was revealed that a portion of his shell had been hacked off too. But in Fast Forward and Back to the Sewer the injury was removed.
 * Occasionally the damage on his shell would disappear, this can largely be attributed to animation errors.
 * Has expertise in blacksmithing, as he was able to forge new katanas with the help of only Raphael in The Monster Hunter.
 * He sometimes rides a foot-propelled scooter.
 * Leonardo has been shown to be somewhat naïve, when he ignores Raph's skepticism and trust enemies such as Shredder and Karai.
 * Favorite music is: Traditional Japanese and New Age.
 * Favorite book is "On the Art of War" by Sun Tzu.
 * His favorite foods are rice, fish, salads, apples, and pizza.
 * Super Power Struggle is the only episode where Leo doesn't appear.