Factual error: The camera starts out-of-focus looking down a crowded sidewalk full of background actors in period clothes and hairstyles (1973). As the camera racks into focus, Sam is walking toward the camera with many awnings visible in the background - a large blue one reads "24 Hr ATM". Though versions were invented prior to 1973, they didn't come into wide usage until the mid-to-late-80's and certainly weren't available in East Village bodegas at the time of this episode.
Continuity mistake: In the series finale, "Life is a Rock," broadcast on ABC 4/1/09, about half-way through the episode, Det. Sam Tyler is approaching a boat, searching for his younger self. In his hands is an M-14 rifle he has taken from a thug. He goes on board, enters the cabin, spots the child Sam Tyler, and sets the rifle down. A minute later, he picks up the M-14 and goes back on deck. In the next shot, however, he's actually holding an AK-47, which gets kicked out of his hands and into the water.