At the beginning, Walt breaks his bacon into pieces and makes it into 52, referring to his age. In Pilot (2008), Skyler made his veggie bacon into a 50 for his 50th birthday.
The Cadillac that Mike drives to meet Walter and Jesse (and abandons afterwards) is the same car that Jesse took from the Cartel party in Salud (2011).
This is the shortest episode of the series.
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 first act of both this premiere episode and the season 4 premiere are set at a Denny's restaurant.