DH didn't tell me exactly how the conversation went down, but I got the impression that Thing 1's classmate invited him. My guess would be something along the lines of he asked for a sleepover, she said okay if it was okay with his friends' parents, then he came to school and invited his friends, my son and another little boy. I could see the conversation going in that direction with a small child. Kind of along the lines of "Hey, Mom, can we do X?" Mom replies maybe or we'll see, the child hears "yes" and later it becomes "But you PROMISED!" KWIM?
Classmate probably got the sleepover idea from TV or an older sibling, asked about it, then did some inviting before Mom knew what she was in for. Then how do you uninvite?
I don't know for sure, but I could definitely see it going down that way.
This is the last week of school before Christmas vacation. Hopefully it will all be forgotten by January. (yea right...Thing 1 has an AMAZING memory...when he wants to) Last year, he was 3, and I had told him at the beginning of December that he could stay at school for lunch one day if he had two good weeks in a row. I didn't realize that there was no lunch at school the last week before vacation. He had his two good weeks, but didn't get to stay for lunch because there wasn't any that day. Nothing was said about it over vacation, but his first week back in January he reminded me that he got to stay for lunch because he had two good weeks!!