Some patients reported that the hospital billing system was a nightmare. They received unexpected and confusing bills. There were charges for services they didn't receive or were overcharged for common procedures. It added a lot of stress to an already difficult situation of dealing with illness. Also, the food provided to the patients was of very poor quality. It was often cold and unappetizing, which is not good for patients who need proper nutrition to recover.
It could be that the sweatshirt has some special significance. Say it was a gift from a very important person or it represents a memorable event. So when it comes to that particular sweatshirt, there's no more to be said, it's just 'end of story'.
It might mean that the sweatshirt is the final or most important thing in a situation. For instance, in a clothing collection, if someone says this, it could imply that the sweatshirt is the standout piece and no other item is worth mentioning.
I'm not sure specifically what the 'Animal House Sweatshirt Story' is about without more context. It could be a story related to an animal house, perhaps a fraternity or a place full of animals, and the sweatshirt might play a significant role in that story, like it being a special item or a source of some kind of adventure or memory.