When Walt is at the Hmong's party, he pats the head of a young Hmong girl passing through, causing the family members to audibly gasp. In Hmong culture, the human head is believed to house the soul, and any touching of the head is believed to jeopardize this, and is thus considered very disrespectful.
The "cool medal" the kids find in Walt's basement is the Silver Star, the U.S. military's third highest award for valor in combat. Despite its predominately gold color, it gets its name from the smaller silver star (based on the small silver World War I Citation Star) set inside the large gold star.
Kowalski is by far the most popular surname in Poland, practically like "Smith" which as a matter of fact it means, in adjective form usual in Polish names. (Kowalczyk - Marilyn Monroe's name in Some Like It Hot (1959) is closely related to it - meaning "Smithson"). The name "Kowalski" identifies a person as a Pole.
According to Bee Vang, the Hmong actors were isolated from the rest of the cast and crew. According to Vang, efforts by the Hmong actors to correct the portrayal of Hmong traditions were ignored. Vang has also refuted claims that the Hmong actors were encouraged to improvise. According to Vang, when he tried to improvise Clint Eastwood told him to "stick to the script". Vang also stated that the cast and crew had a baseball game but the Hmong actors were not invited. It was assumed that the Hmong actors were immigrants and did not know about baseball. But Vang states that the majority of the Hmong actors were US natives.
Walt Kowalski's gun collection seems to consists of weapons he used in the military. His rifle is an American M1 Garand, a 9.5lb .30-06 gas-operated rifle. It was first issued during WWII, then re-issued in Korea before being phased out by the M14 selective fire .308 rifle. His pistol is an M1911A1, a .45 ACP semi-automatic handgun also issued during the Korean war.