The film The Princess Bride (1987) and Mandy Patinkin who portrayed one of the main characters (Inigo Montoya) is mentioned frequently throughout the entirety of this episode. Marshall and Ted citing famous lines of Inigo Montoya during their sword fight, as well as Lily when she is fighting with Robin. Robin also mentions Mandy Patinkin several times as being a magical phrase attracting old people. She and Barney use it to gather their elderly relatives.
Mandy Patinkin is an actor known for roles in The Princess Bride, Chicago Hope, Criminal Minds, etc.