It sounds like your friend was overwhelmed and did go overboard. Speak to your chosson first and tell him that in the future he should please come to you if anything like this happens again because they don’t know you as well as they think they do and at best they want you to have what they would like to have. So he should check these things out with you first because you don’t want anyone hitting him up for money making him feel that he is doing it for you when it is really doing it to appease their need. It is better that the two of you don’t keep secrets from each other. So the best thing would be for him to say “I’ll think about it and get back to you and then discuss it with you”. This way you can appreciate the fact that your friends want the best for you even though you are angry that they would go to such lengths to get it, you can put an end to it by coaching your chosson how to stop it. In other words he can say “I asked “C” if we registered for kitchen appliances would she choose this or this and she laughed at me and said I would never use ….”
In this way he can guide them back into normalcy and tell them they should really ask you what you want before they make themselves crazy and stress you out in the process.