what if I wear a costume on my friend's wedding

[simone333]

The story goes like this:My best friend's wedding is coming in the next month.She is fond of the spider man.I hope to send her a costume as a gift ,but she asked me to wear a costume that day instead of sending it to her.However,I am worry about whether it is appropriate for me to wear a costume (dress up as a spider man) at her wedding.As her parents ,friends and the groom's parents will all be there.I am very contradictions ,on the one hand ,I don't want to let her down.On the other hand,I don't want to do something wrong in such an holy occasion.
So ,please do give me some suggestions about this.Or what do you think of some people wear a costume at a wedding?