Continuity mistake: When Marshall and Lily approach the reception desk at The Wedding chapel, Marshall's cocktail moves from his right to his left hand instantly between shots. (00:07:55)
Continuity mistake: At the courthouse, we see Marshall, Lily and Barney walk around the corner towards the bench twice, from two different angles.
Continuity mistake: At the courthouse, when Lily is eating red licorice from the vending machine, the piece she is eating gets longer between shots.
Chosen answer: She was finally shown at the very end of the last episode of season 8, continuing into season 9. The actor's name is Cristin Milioti: http://www.imdb.com/name/nm2129662/.
Knever