Barney, Ted and Robin: Yeah. Both Marshall and Lily: Unpronounce us! Lily: The wedding chapel... Lily: We're going to Atlantic City to elope.
Plan: A: Atlantic City; Q: Where do Marshall and Lily decide to elope to? A: the wedding; Q: What do Barney, Ted and Robin decide to take part in? Summary: Marshall and Lily, together again, decide to elope to Atlantic City, and they gather Barney, Ted and Robin to take part in the wedding.