During the Bryn Mawr College (located outside Philadelphia, PA) reunion scenes, numerous references are made to the Piggly Wiggly supermarket chain. While the chain's name lent itself to numerous comic lines, Piggly Wiggly is located in the southern US and has NO stores in the Philadelphia metro area.
When Midge and her classmates are reading the notes from their future selves, one of them mispronounces Kahil Gibran's name (with a soft G).
At the beginning of the flashback to Joel and Midge's fight in the taxi, the chryon identifies the year as 1955. After the taxi stops and Midge gets out and starts to walk away, there is a 1957 Chevrolet Bel-Air parked behind her. The taxi itself is shown to be a 1963 Checker Marathon (based on the amber blinkers and quad headlight array). In 1955, most New York taxis were either a DeSoto Skyview or a Checker A6, both with dual headlight arrays.