The song that Robin Williams and James Wolk, 'Drive Thru Lovin'' to 'Kelly Clarkson', was completely improvised.
The character of Zach Cropper (James Wolk), was described in the script as "George Clooney, only better looking and more charming."
Sarah Michelle Gellar (Sydney) was sued by McDonalds in the early 80s after she appeared in a Burger King commercial that mentioned McDonalds by name. The case was settled out of court.
Reference is made to selling a lot of "hamburgers and reasonably-sized soft drinks." This is very likely a jab at NYC's recent attempt to ban the sale of sugared soft drinks larger than 16 oz. The ban would have been applied to restaurants, food vendors, and movie theatres, among others, but not to groceries and bodegas. The proposed ban also did not seek to ban free refills.