It is wrong to go somewhere without being invited.
Susan's friend Marissa is getting married soon but Susan still hasn't received an invitation.
Susan wants to attend Marissa's wedding.
Susan drops subtle hints to Marissa about her desire to attend the wedding.
Susan shows up to the wedding unannounced without having been invited.
Marissa ends up inviting Susan to the wedding, and she has a great time at it.
Susan is denied entry to the wedding because she isn't on the guest list.