Pam states that there are no staff birthdays coming up in the next month: Meredith's is the next one, and it's still a month away. Later in the series, in episode 7 of season 4 (Survivor Man), Angela lists the birthdays that month,in order: Kelly, Creed, Oscar and Meredith.
In the end of the episode, when Roy catch Jim "flirting" with Pam, Jim reveals that they was just messing around with Dwight. At that point, Dwight had not yet dyed his hair. Next scene, Dwight has dyed his hair blond, although knowing they were pranking him.
In a scene from "The Alliance" between Jim and Dwight you can see one of the employee's car's license plates. On the show, their plate is 8326-FLO. In Pennsylvania, standard plates are three letters then four numbers (ex. AAA-1234).
In The Office season 1 DVD, when you view the synopsis for "The Alliance" it claims that Dwight wants "John" to join the alliance. Dwight and Jim form the Alliance - John is the real name of the Actor who plays Jim.