I've ever seen/heard of this done.
One of my co-workers is getting married in October and we got our invitations in the mail the other day. Well today we had dinner at another co-worker's house and she also is invited to the wedding. She had her invitation laying on the counter when we walked in and it was different than the one we got, at least appearance wise it was. The wording was the same. We were both invited to the reception.
Is this a common thing for people to do? I always thought you ordered one type and sent that to everyone.