Donatello is the third eldest in all of the turtles. He is one of the main heroes of the series.
Donnie has a way with machines and is the most intellectually inclined of the siblings. Of all of the turtles, he has devoted more of his time to non-combat oriented pursuits such as the study of technology, biology, chemistry, mathematics, and metallurgy. Donnie is the 2nd most mature out of all his brothers, aside from Leo, trying to be the voice of reason and logic. He is very protective of his siblings and is willing to do anything for them. Donnie is somewhat a sci-fi geek, aside from Leo...though he's more of a tech geek. He will often go off on technological rants that his brothers either don't understand, don't care about or both.
Donnie is a skilled martial artist but often puts more faith in his gadgets and machinery than the more traditional methods taught to him by Master Splinter.
Donnie is a mutated turtle with brownish green skin. Donnie has a gap in between his teeth. He wears a purple mask where the tails of the mask are longer than any of his brothers, except for Raphael's. Donnie is the tallest and the thinnest of his brothers. He has brownish red eyes, looks more professional, quiet, and handsome. he is good with machines and is talented of making new technology for his brothers. But there's one thing he hasn't gotten right... getting April to notice him. In his horse form, he wears a purple feather headdress that replacing his purple bandanna/eye mask and purple saddle on his back that replacing his turtle shell. However, after the spell breaks at dawn, he was ultimately turned back into his normal form.
Donnie's intelligence, determination, range and will-power makes him a great asset to the team. His weapon of choice is a bo staff, matching power, speed, and range. He often tends to fight in a more traditional martial art style emphasizing on redirecting enemy blows and defending until the optimal time to strike presents itself. Though his weapon is not as strong, or not as skilled and formidable as Leo or Raphael, or not as gifted as Mikey, Donnie is quite capable of holding his own against tough opponents and prefers to use kicks (just like in his horse form) over punches since he is not that hard of a puncher.
Donnie is stealthy like all his brothers, and like them he can hide in the shadows, sneak around without being detected, and use hand to hand combat like a real ninja.
Donnie loves Master Splinter, as his father, but he sometimes questions his wisdom. Splinter praises Donnie for his intelligence and skills as a ninja, but wishes for him to think a little less in battle. He even hugged his father when he came to his senses. Like with the others, Master Splinter is very protective of Donnie.
Donnie usually is the peace maker between his brothers, never starting fights and always tries to stop them when they get out of hand. His only problems with his brothers are Raphael's temper, Mikey's immaturity, Leo copying things he see's off "Space heroes", and when they all don't act like the appreciate his intelligence. His brothers often get annoyed with him when he acts like he knows everything. Despite everything, Donnie loves his brothers as much as they do him, and he often tries to help them out, back up his two oldest brothers, Leo and Raphael, and protect his little brother Mikey from any sort of harm that comes their way.
His best friends are his brothers, Jackson Jekyll/Holt Hyde and Ghoulia Yelps. He is also a good helper of Draculaura. He is also consider Timothy as his friend, even he was tried to melt Raphael's face.
He has a crush on April.
- His favorite subject is "Mad Science".
- He understands how Jackson feels when he gets bullied.
- He hates magic for a little.
- He believes that everyone in Monster High are mutants.
- He's never understand why Abbey speaks in Russian accent while her birthplace is in Himalayas.