At lunch on the first day, DJ and Kimmy encounter Kathy Santoni but they say that they cannot recognize her at all. This makes no sense. Kathy's body may have developed significantly over the summer, but it is not possible that she would be unrecognizable by her face/hair and voice from just 3 months worth of time passing.
When Joey steps on the grass to put down the practice golf ball, the grass squishes under his feet, indicating it's fake.