Alexis accidentally has a party the night Castle dresses up as Elvis. The next morning, the money exchange happens. Castle, Esposito and Ryan are given that night off, and Castle doesn't return home until the next morning. Alexis is still frantically cleaning up after the party more than a day after she expected Castle home.
When Castle, Ryan and Esposito first arrive and walk through the casino, there are 2 women in tight dresses walking away from them. The camera cuts to various angles showing the same 2 women walking in several different directions in the background. (Brunette in brown dress and Blonde in purple dress.)
When the boys are told they're going to Atlantic City, Ryan checks his watch. The next time we see him, he checks his watch again.
When Castle asks Daniel to look him up on the system, the results on Castle's appearance appear to be wrong. He is listed as having brown hair and brown eyes but Castle has brown hair and blue eyes.