The name Edwin Jenner, the doctor at the CDC, is a reference to to Edward Jenner who developed the first vaccine (which was for smallpox).
Daryl Dixon, unlikely fan favorite of the show (played by Norman Reedus) uses a specific type of crossbow, a Horton Scout HD 125. This thing retails for about $300.00 (US) and Reedus has said that he takes it home with him after filming.
In an online interview, it was revealed that Frank Darabont envisioned having several self-contained episodes that would not continue the main story. One such episode would have been the season two premiere. It would have involved Sam Witwer (who Darabont used in The Mist and played the tank zombie in the series premiere) as a solider in a Black Hawk Down style Atlanta. Witwer would have encountered several of the cast before being bit and locking himself in the tank.