Donatello's twin brother died a few years ago and something in him changed, he blamed himself for Leo's death. He would constantly act distant and become extremely protective over his brothers, people would hear him 'talking to Leo' and they called him insane or said he wasn't letting Leo go but it sounded bad. Do,nnie would beg 'Leo' to let him be himself but apparently Leo wouldn't let him, Donatello would have night terrors and would fight with 'Leo' all the time but it never stopped. People just called him crazy and began ignoring these issues, even his brothers. They still cared but couldn't help him

One night Donatello woke up from another night terror, tears streaming down his face and he kept begging 'Leo' to stop. A silhouette of 'Leo' sitting on his bed next to him smiling widely, an evil look in his eyes. Nobody but Donnie could see him.. at least that's what he thought "Just let me be who I am!" Donnie yelled "That's what you really need to understand, and I hope so hard for the pain to go away!" Donnie cried, 'Leo' just smiled wider as if feeding off Donnies pain