The rules that Homer "reads" do not match what is typed.
As Wally and Candy arrive at the orphanage, Curly can be seen running down the steps to approach their car. He looks as if he's helping to open the door, directly in front of Candy. However, in the next shot Curly is seen running in from the left to introduce himself to Candy.
(at around 54 mins) Dr. Larch says Homer graduated from college in 1935. In the end scene, Homer looks at his Bachelor of Science diploma with the Roman numeral for the year which is 1934 (MCMXXXIV).
When Wally, Candy, and Homer leave St. Cloud's for the first time, Candy is lying down in the back seat. When they drive down the dirt road, she is sitting up. In the next shot, she is lying down again.
Several wooden lobster traps, including the one that Candy picks up, have no cement weights at the bottom, making them unusable.
In the end credits, the town of Lenox, Massachusetts is spelled "Lennox".
When Homer is learning how to pick apples, a string is clearly holding an apple onto a branch. When he picks it, the string dangles from the branch.
When the orphans watch King Kong (1933), the giant ape peels off Ann Darrow's clothes. That scene was cut shortly after the premiere, and was not publicly available until 1971.
The scenes at the drive-in feature a full cinemascope-sized screen. Cinemascope was not available until 1953.
The package containing Homer's doctor bag bears four examples of a stamp honoring railroad engineers that was released on April 29, 1950.
In the last scene, at the railroad station, railroad cars from the 1960s or later are on the adjacent track.
Early on, a round "isolation tent" with a clear plastic window is hanging over a bed. That clear plastic was not was invented until years later.
When Candy and Homer are visiting the beach, breaking waves can be heard, but the sea is calm.
As the train pulls up to the station at the beginning, the clang of the bell on the train corresponds to the engineer pulling the lanyard to swing the bell except for the last clang, when the lanyard is not pulled.
When Homer talks to Rose while she is doing the dishes, an actor's mark is visible on the floor.