The crystal meth seen on the show is usually large sugar crystals or rock candy. This is also the case for scenes where characters smoke meth.
In the show Walter Jr. has cerebral palsy. RJ Mitte, the actor who plays Walter Jr., has a mild case of cerebral palsy in real life.
Once Walter starts cooking meth he decides to go by the pseudonym Heisenberg. This name is a reference to Werner Heisenberg, a German theoretical physicist known for his Heisenberg uncertainty principle.
The first two episodes of season 2 were originally supposed to be the final episodes of season one. The episodes were already fully completed but the 2008 writer's strike kept them from airing until season 2.
During season two, four episodes started with flash-forwards to the plane crash that ends the season. The titles of all of these episodes come together to form the message "Seven Thirty-Seven Down Over ABQ".
Ep. 1 Pilot The term "breaking bad" is a southern phrase used to describe someone who is going down a bad path. Jesse uses this term to describe Walter in the Pilot.
Ep. 13 ABQ During this episode Jane's bedroom is shown and it has a large mural on the wall. Included in the mural is a pink teddy bear similar to the one that lands in Walt's pool at the end of the episode.
Ep. 8 I See You The title of the episode, "I See You", is a reference to the fact that by the end of the episode Hank is in the intensive care unit (I.C.U.).
Ep. 10 Fly An homage to Pulp Fiction when Jesse is looking for something to break the door down. He gradually finds larger things on a shelf. Much like Butch finding objects in the pawn shop.