I came across this interesting fact about Walter
Brennan had already worked in vaudeville when he enlisted at age 22 to serve in World War I. He served in an artillery unit and although he got through the war without being wounded, his exposure to poison gas ruined his vocal chords, leaving him with the high-pitched voice texture that made him a natural for old man roles while still in his thirties.
The youngest I have ever seen him is Two Fisted Law were he has dark hair.
