Continuity mistake: Meg Ryan and the bloke she was going to marry first were picking out colours for the house and he points to one but when he mentions later on he points to a different one.
Factual error: The comet is seen to move rapidly across the sky. This in actuality never happens as they are so far away. The speed shown in the film is more appropriate for a shooting star.
Continuity mistake: Towards the end, when Tim Robbins is chasing the President's car, he stops by Einstein's house first (he is wearing a red jacket). When they show a close up of his hand knocking on the door, his sleeve is blue. When they cut back out, it's red.
Continuity mistake: When Meg finally realizes her feelings for Tim she puts her legs on his lap. The angle changes and she does it again.
Continuity mistake: When Tim Robbins and Meg Ryan are on the balcony looking at the stars, the camera is doing a shot from the front - Tim is on the right and Meg is on the left. The camera then does a shot from behind them and Tim is still on the right and Meg is still on the left.
Factual error: At the reception after Ed Walters delivers his fake scientific lecture, Miss Boyd is congratulating him and pesters him for more. She asks: "Do you know, I believe that you used DeBroglie's formula for the length of the pilot wave. I forgot that bit. Could you remind me?" So then Ed clumsily responds by way of secret signals from Einstein & company. What they relay to him is x = w^3/pi, but this has no relation to DeBroglie's formula.
Continuity mistake: The scene where he gives his lecture before being called out you can see 3 small measuring instruments on the wall on the right below the board. Once Ed begins to mumble during his lecture there are only 2 instruments on the wall, and they've been moved.
Factual error: Following his lecture on cold fusion, Ed Walters attends a reception, mingling with the academic crowd. At one point, millionaire Louis Bamberger approaches Walters and excitedly presents him with a Bic 4-Color Ballpoint Pen, which suggests that the pen was new on the market in the early-to-mid 1950s. Problem is, the Bic 4-Color Ballpoint Pen wasn't invented and marketed until 1974, some 20 years after the setting of this film.
Continuity mistake: When Meg, Tim, and Walter are on the sailboat, from one angle (facing forward) the water is smooth whereas from the other angle (facing aft) the water is choppy.
Factual error: When Albert and 'the boys' are driving around in one scene, 'Tutti Frutti' is playing on the radio. Tutti Frutti wasn't released until November of 1955. Albert died in April that year.
