Factual error: When the TV store is closing at Bloomingdale's, The Richard Simmons Show is shown on the monitors. In 1984, when the film is set, this show was broadcast only in the morning and was not released in syndication. The show would therefore not have been playing on a television channel in New York City in the late evening.
Continuity mistake: At the beach, Walter and one of the twins carry a box and are inches away from the boat. Half a second later, when the angle cuts to Allen asking the other twin, the first couple is standing behind, far from the boat, holding the same box and repeating the previous movements.