This story reminds me of my 5th grade class. There was one boy who had absolutely no friends. I don't think he was autistic, but he was was not liked for whatever reason. He wasn't cool, he was chunky, etc. I was okay with him but I wasn't friends with him. I didn't think he was funny and he tried too hard. But I was never mean to him.
When his birthday came up, he invited everyone in class. The kids I knew told him they were going before hand. Since they said they were going, I decided to go too. On the day of his party at his house, I was the only kid who showed up. The entire house was decorated from top to bottom and the only people who were there were the boy, his parents and myself. I could tell he was sad and disappointed. But he and his parents put on their best happy face and tried to entertain me, since I was the only guest there. I was stuck there for about 3-4 hours because my parents dropped me off. I felt so awkward. His mom and dad seemed like really good people so I tried my best to have fun alongside.
One day when the kid wasn't there, our teacher had admonished the entire classroom for picking on him. She couldn't understand why everyone hated him so much. I felt bad about it but I was surprised at how everyone else wasn't.