In the movie, Kirk is told that Molly has a defect which turns out to be syndactyly, or as it is more commonly called, webbed toes. In reality actress Alice Eve, who plays Molly, has heterochromia; her right eye is green and her left blue.
During the scene where Kirk's friends are teasing him about his premature ejaculation, Jack's hamburger can be seen to have french fries on it. This is a custom local to Pittsburgh. Sandwiches are famously served that way at Primanti's, a popular Pittsburgh eatery seen earlier in the background during Kirk and Molly's date where they meet Cam.
Jay Baruchel, who plays an avid Pittsburgh Penguins fan in the movie is actually a huge hockey fan, and said "I get starstruck and kind of lose my faculties, when I meet hockey players and, especially, Sid," when referring to meeting NHL star Sidney Crosby.
The double-date at the hockey game was filmed at an actual NHL game on March 27, 2008 between the Pittsburgh Penguins and the New York Islanders. Pittsburgh won 3-1, although the score was actually 2-1 at the end of the 2nd period, not 3-1 as depicted in the film.
When meeting Molly, Dylan asks her (trying to understand why she's dating Kirk), "Did you hit his car?" In Crossing Over (2009), the character played by Alice Eve, an illegal immigrant, is forced into a sexual relationship with an immigration officer, played by Ray Liotta, after hitting his car.
During the scene at the airport with Kirk, Marnie, and his friends right before his double-date with Molly at the hockey game, if you look carefully, you can see Kirk has Molly's iPhone in his hand. That's because it was originally supposed to be earlier in the film right after he finds her phone. It was moved in editing.
Jay Baruchel's sister is a big fan of NHL star Sidney Crosby. In an interview Jay said that after he called his sister to tell her about meeting Crosby "she has never been more impressed with me" and he had to take the phone away from his ear "because of the screaming"
While at the airport, comparisons are being made between Kirk and Molly and romances between other couples. One of the romances noted is between Stephen Hawking and his nurse. Alice Eve, the actress who plays Molly, played a small part in the biographical drama, Hawking (2004), based on Stephen Hawking's life.
The scenes at the air show were filmed at the 2008 "Wings Over Pittsburgh", an annual event at the U.S. Air Force Reserve Base in Moon Township, a suburb of Pittsburgh. It was canceled in 2009 due to military manpower and resource limitations, but held again in 2010.