During the shooting of the cab scene, Jason Segel's (Marshall) script didn't tell him the real news, but instead it said the Lilly was going to say she was pregnant. Therefore, Marshall's reaction is actually Jason Segel's very real reaction. The producers of the show did this because the show focuses on milestones of young adult life, and they wanted to make the shock and dismay of unexpected events such as that scene very real.
There is a countdown throughout the episode - from 50 to 1. The countdown is as follows: 50 - On a pamphlet in the Doctor's office in the first scene 49 - Same pamphlet on the Doctor's desk ("months later" according to Ted) 48 - Label on hot sauce Marshall uses at MacLaren's 47 - Barney's laser tag forms are for the "47th Annual" Laser Tag Competition 46 - Printed on Dr. Stangel's certificate behind Lily when they first meet 45 - 45¢ the price of the hot wings at MacLaren's 44 - Number of beers on tap, on a circular blackboard in MacLaren's 44 - (appears twice) Football number on a man's jersey in MacLaren's 43 - On the pamphlet Marshall is reading in Dr. Stangel's office 42 - Second side of the same pamphlet 41 - Race car poster number in Dr. Stangel's office (which disappears when Marshall goes back) 40 - Ted's book that "New York's 40 greatest landmarks" when Robin comes home from Day 1 39 - Number of office behind Robin 38 - On the back of Robin's co-worker's newspaper, 38° in the weather section 37 - Lily is reading a Decadence magazine with the "37 Recipes for Holiday leftovers" title on it. 36 - The number on Marshall's dad's beer, "Old Number 36" 35,34 - Stock markets are up 35.34 points on Robin's news screen 33 - Miners rescued from collapsed mine on Robin's news screen 32-27 - On Robin's screen: "Today's lottery numbers are 32 31 30 29 28 27" 26 - Marshall's dad is reading "26 Home Improvement Shortcuts" 25 - Textbook that Ted is reading in the apartment, "25 Greatest Bridges" 24 - One of Robin's co-workers is reading a magazine, with a sports player on the front with "24" on his jersey 23 - Metro News 23, the channel Robin says "I'm a dirty, dirty girl" on 22 - Seen in the corner of Robin's Japanese broadcast 21 - Calendar behind Dr. Stangel 20 - Room for masturbation room at Dr. Stangel's office 19 - "Top 19 Nekkid girls countdown" on Nekkid magazine in the room 18 - Apartment number of Marshall and Lily's apartment 17,16 - Marshall's specimen cup seen in his apartment 15 - Grams of fiber in Robin's cereal 14,13 - Apartment number of Sandy's apartment 12 - The book "12 days of Christmas" behind Marshall when he's speaking with his parents in their apartment 11- On Ted's architecture book, "America's 11 greatest water towers" 10 - On Robin Sparkles left jacket arm when shown to co-workers by Robin 9 - Disguised Barney holds a folder when talking to Marshall 8 - Number on Dr. Stangel's door 7 - Number on Marshall's champagne bottle 6 - Dr. Stangel turns the folder with the 9 on it upside down 5 - Barney gives Marshall a "Motility 5" 4 - The "4 Layers of the Uterus" poster in Dr. Stangel's office 3 - "Open til 3 am sign" outside MacLaren's 2 - Clock in Marvin Sr's wood shop 1 - Number of the cab Lily arrives in
Neil Patrick Harris is credited twice for this episode, once in the opening as a member of the main cast and once at the end as "Dr. John Stangel."
The glasses Barney is wearing in Dr. Stangel's office are The Sensory Deprivator 5000 that Ted invented in the season 2 episode Monday Night Football.
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