Old Joe compares the feasibility of Walt's mobile super-magnet to that of "string theories and God particles", in this episode first broadcast July 12, 2012. Just eight days prior, on July 4th, the actual long-sought "God particle" (the Higgs boson) was detected for the first time by the Large Hadron Collider on the Franco-Swiss border.
Throughout the entire series, Vince Gilligan uses symbolism with the characters color of clothing. In the beginning of the episode, Walt is wearing a green shirt when he kills Gus and when he gets home. The color green represents greed, jealousy, ambition and growth. After he cleans up everything he used to make the bomb, he changes into a blue shirt. Blue represents royalty. Symbolizing the crown has switched hands from Gus unto Walt.
The trivia items below may give away important plot points.
In the Season 5 premiere's opening scene, Walter White is shown having a gloomy 52nd birthday breakfast at a Denny's in Albuquerque while showing a New Hampshire drivers' license with the last name Lambert, coughing and taking medicine, not wearing a wedding ring, and paying a gun dealer who was seen in Season 4's "Thirty Eight Snub" for an M60 machine gun. In an August 2012 Rolling Stone article about the 5th and last season of the show, Bryan Cranston revealed that Vince Gilligan told him a few key facts about this scene: Walt was returning to New Mexico from New Hampshire by himself, he had come back and gotten the machine gun to protect someone, and his cancer is "possibly" no longer in remission.
At the start of the show, they show a car Walt has been using whilst on the run. The registration is 3272153. This is the SID number for methamphetamine on PubChem, a database of chemical molecules maintained by the National Center for Biotechnology Information.