Continuity from previous episode - In "Homecoming" Charlie serves Hiro, looks to the right and passes customers at a table to greet her friends at her party, she beckons Hiro before she gets to her friends. In "Six Months earlier" she turns to the left, beckons Hiro before she gets to her friends and passes an empty table to the right.
The EEG monitor that Gabriel is hooked up to is scrolling way too fast, too fast to be interpreted live at least. EEG normally scrolls much slower, especially if real-time interpretations are to be made.
At Peter's graduation party, the song "Smile" by Lily Allen is played. This song was released in July 2006 and was therefore not available "six months before" when the episode takes place.