How To Handle Unexpected Guests At Your Wedding:

It's important to make known there are limited seats and plates but that you will try your best to accommodate them. If the person genuinely should not be there and has no connection with anyone, kindly explain to them that your event is RSVP Only and ask them to step aside. From there let your event staff or security take over.  

Avoid reacting with visible frustration and stay calm. If you’re unsure who they are, discreetly ask your coordinator or mutual friend if they were invited or are connected to someone at your event. If they turn out to be a friend of a friend and you decide to let them stay, you might just end up with a story worth telling.