The jersey that Marshall wears bears the number "70". The only player in Minnesota Vikings history to wear that number is Defensive End Jim Marshall. Marshall was a member of the Vikings' famed "Purple People Eaters" defense. His number was retired by the Vikings in 1999, the same years as the NFC Championship loss mentioned prominently in the episode.
The jerseys people wear at the bar read the following names (in order of apparition): Bays, Thomas, Tatham, Smulders and Fryman. These are last names from the cast and crew: Carter Bays and Craig Thomas are creators and executive producers, Chuck Tatham is one of the show's writers, Cobie Smulders is the actress who plays Robin and Pamela Fryman is one of the executive producers.
This is the only episode where we actually see Ted's sister Heather.
In this episode, Ted tells Barney, "You're like Weird Al Yankovic if you only wrote Christmas songs about banging my sister," to which Barney replies, "First of all, I'm flattered..." In "Noretta" (S07E07) Ted is trying to get someone to go see Weird Al with him, and when he asks him, Barney hangs up on him.
In the scene where 'Robin Scherbatsky' talking to all of the Minnesotans in the bar, there is a person standing in the crowd wearing a football shirt with "Smulders" written on the back. Smulders is the real surname of the person who plays Robin.