Chloe (Allison Mack) sported a distinctive asymmetric hairstyle, a style Mack had adopted over the summer hiatus. However, it was felt that the look wasn't right for Chloe, so Mack wore extensions for the subsequent few episodes whilst her natural hair grew longer. Mack has often joked that no one in Smallville appeared to notice Chloe's hair changing length over the course of one episode.
In the commentary for this episode, it is mentioned that the pre-credit scenes of Clark having fun with the Red Kryptonite (Destroying ATMs, etc.) were added in a week before the episode aired. Gough and Miller were all for the idea as long as the network paid.
Terence Stamp, the voice of Jor-El, played Gen. Zod in Superman I & II.
At the beginning of the episode, Clark runs into a phone booth and rips open his shirt to reveal his 'shield' burn pattern, reminiscent of Clark Kent running into a phone booth and changing into Superman, revealing the "S" on his chest as in the DC Comics lore.
While being erased, the mark on Clark's chest in the final split second resembles the "S" sign that Superman will wear in the future.