Originally intended as a serious movie, this film was altered by Harold Lloyd into a comedy by adding the gag scenes later on.
Harold is seen preparing the detached collar for his shirt. Detached collars were much easier to clean and press than cleaning and pressing an entire shirt. Detached collars were held to the shirt by two studs, one in the front and one in the back. The collars were made of cotton or linen that was heavily starched or attached to a stiff celluloid strip. Celluloid is very flammable.
This was one of Harold Lloyd's earliest box office hits, which helped make him one of the silent era's most popular stars. On a budget just over $94,000, Grandma's Boy grossed over $1 million, placing it among the biggest money-makers of 1922.
The flashback scenes set in the Civil War are actually the original short around which this movie was built.
The sheet music His Girl plays is "You Are the Ideal of My Dreams" by Herbert Ingraham; it was published in 1910.