Donnie and Splinter in “Unfinished Business”

Donnie

I'm sorry, Sensei. This is all the retro-mutagen I have left.

Splinter

I may not be human, but I am fortunate enough to have my humanity. Save Kirby.

[As Donnie leaves, he looks down at the black-and-white picture of his original human self and his late wife, Tang Shen, with their infant daughter Miwa between them.]