Ok, I just had a moment of sudden, amazing, absolutely heartbreaking realization.
When the Turtles go back to the lair, Donnie tells everyone to grab one meaningful thing.
Raphael grabs his photo of Spike. He takes Donnie’s comment literally and grabs what is full of sentiment and meaning.
Mikey takes Ice Cream Kitty and some frozen pizzas. He brings a sentiment object (Ice Cream Kitty) and a useful object (food).
But, Donnie; Donnie brings supplies. Not food or weapons, but gauze, band aids, a couple of test tubes, and a beaker. He brings no sentimental object because this this will help him take care of what means a lot to him. Who do we know that is incredibly banged up and is in need of medical supplies? That’s right. Leo. He could have brought his computer, but no. Donnie brought supplies to take care of Leo and make sure he is ok and taken care of.