During the scene where the manager comes to the house, passing all the news crews, the door of the house has three small windows in descending order. Once inside the house with Rocky's wife the door in the background has an arched window instead of three small windows.
In the final fight against Tony Zale - Zale steps forward and takes off his robe twice.
When Rocky orders the black-and-white soda, a spoon suddenly appears as he's handing back the glass for more seltzer.
In the scene where Rocky is flying to New York from Chicago, the picture of the plane in flight is reversed (see the airline name in backward lettering). It was probably intentional so that the plane would be heading from left to right. That is the way people would imagine the plane heading, since that's the direction on a map.
When Norma asks Benny for directions how to get home after meeting Rocky in the early 1940s, he tells her to take a Subway route that did not exist until 1954.
Graziano's second fight with Tony Zale took place on July 16, 1947. Like many 1950s movies that depicted earlier decades, they were a little sloppy about women's fashions. In scenes just before the climaxing fight, Pier Angeli is definitely wearing a 1950s-style sheath dress.
Much of the location shoots in New York show the tenement where Rocky grew up next to the Manhattan Bridge, but his address on East 10th Street is over a mile north of the bridge.