(Based non @cupcakeslushie on tumblr!!)
Time moves differently in the prison dimension. Leo was gone 3 minutes in the real world, but Leo experienced 3 years in there. Due to that he was... A little insane. Feral. While he was there, he hallucinated his brothers...
Leo first came out, covered in blood and scars. His eyes were slits, he couldn't speak all that well, had long uncut nails, ratty disgusting clothes. He had broken bones, A broke shell, and a broken mind. All he had was a photo. He called it his treasure.. His sanity. Mikey was still in the med bay, recovering his cracked arms. Raph was out getting groceries.
Leo was hissing and thrashing as Donnie held him, attempting to bring him to the bath.
Donnie grumbled. "He better not have rabies." He has already been bit 5 times.
Casey was trying to calm him down, but was too skittish to get close. "Sensei, if you want to see master Michelangelo, you need a bath! He can't afford the infection."
But finally, they got him in the bath. He calmed significantly, but he didn't bother closing his eyes when he submerged under the water. They stayed wide open.