Possible goof
The girls take the invitation to Natalie's debutante ball and run to the photocopy place at the mall and ask for 150 copies to be made. Then they run into the streets and pass out the invitations to every punk they see.
The goof is that the camera shows some closeup shots of the invitations, and they look exactly like professional wedding invitations that were printed. The "copied" invitations even have the fancy white embroidering the way a professional invitation would. If they were just photocopied, they would be on plain white paper.
There's no way the girls would have had the money to pay for 150 printed embroidered invitations. They were supposed to be photocopies, but they look too fancy!