When Walt is flipping through channels while blocking out the sound of Skyler calling his name, one of the channels says "plants for you, better call Saul!"
When extracting ricin from Castor beans it is extremely important to keep external contamination, even at the germ level, out of the process. That is the reason Walt is so careful about touching the raw beans. Ricin itself is not that fragile. It is during the process of extraction that the bean is sensitive.
When Gonzo and No-Doze are originally introduced in season 1, their names are reversed in the credits: Jesus Jr. is credited as 'No-Doze' and Cesar Garcia as 'Gonzo'. At the end of season 1 and for the remainder of season 2, their character names are reversed. In the spin-off, Better Call Saul (2015), both are back the other way round again.
The second season premiered with this episode on March 8, 2009, nearly a year (364 days) after the final episode of season one which first aired on March 9, 2008.
Hank's standard dress code includes a Casio G-Shock on the wrist. The exact model is hard to discern, but the protective bars across the face are a giveaway.