Based on area codes, Barney says that Ashlee is from Nassau County on Long Island (area code 516), even if she might dress like she's from the New York City boroughs of Brooklyn, Queens, the Bronx or Staten Island (area code 718) and act like she's from the New York City borough of Manhattan (area code 212). Barney also says that the woman's husband, letting her out alone on St. Patrick's Day, has to be from Northern New Jersey (area code 973), or else he (Barney) is from Wyoming (area code 307).
When Ted is seen exiting the club after realizing how unhappy he is with his choices, the name of the club is displayed clearly for the first time: 'Low Point'. It's also clearly displayed when talking to the bouncer before entering the club.
When Marshall, Lily, and Robin first enter the new apartment, it is already visibly evident that the place is crooked: the bridge that can be seen out the window is not quite parallel to the floor.
Barney tells Ted "Ted, listen, are you hearing that? That's the universe, the universe is talking to us." To which Ted replies: "We don't have to build a baseball field do we?" This is a reference to Field of Dreams, a movie often mentioned throughout the series.
When Barney walks in wearing his green suit, Ted remarks that he is The Riddler, a villain from Batman comics who specializes in riddles and puzzles. Neil Patrick Harris would later dress up as The Riddler for Halloween with his husband David Burtka and their two children.