I don't think ninja turtles have a human-like penis, after all they are reptiles and you can't see anything even if they walk around pratically naked. But maybe, after a second contact with the liquid mutagen during their battles they could develope even more resemblance to humans. Please, don't hate me for what I did to your heroes but it was just too fun.
Here is Raphael. He is the one that has the biggest balls and it seems that he found something as good as pizza.
Here is Donatello. He is the one with the longest dick and seems pretty amused by the big shlong that now he has between his legs.
This is Leonardo. He has the biggest girth. Maybe he is so angry because he is thinking that will have to start wearing pants. Loose jockey boxer shorts maybe.
Here is Mickey. He is the one who can cum more. He is a dude who like to play, and it seems that he found another use for his nunchaku that he seems to appreciate almost as much as his beloved pizza .
18 hours ago