(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.
Now he's in the lair, huddled under a blanket, growling softly and muttering broken words to himself. Leo rustled around. He started to trust them... Maybe to the point where he'd share food.
Donnie had a plate of strawberries for the poor guy, but he was frankly terrified of getting bit by Leo. He just stood there.