Carrie Anne Fleming was cast as Karen Singer since Elizabeth Marleau, who had played her in season 3's Dream a Little Dream of Me (2008), was pregnant. The producers thought it would be too weird, even for Supernatural, to feature a pregnant zombie. Fleming had previously played a small role season 2's In My Time of Dying (2006), as "Dying Nurse".
This is the first appearance of Sheriff Jody Mills, portrayed by Kim Rhodes, who becomes a semi recurring character in the series.
The agent names the brothers use in this episode are Dorfman and Neidermeyer. Kent Dorfman and Doug Neidermeyer were both main characters in National Lampoon's Animal House (1978).
In an earlier episode, Lucifer Rising (2009), Dean makes a reference to the kids TV show The Suite Life of Zack & Cody (2005). Kim Rhodes who plays Sheriff Jody Mills, played Zack and Cody's mother Carrie on the show.