It was his role in A Guy Named Joe (1943) with Spencer Tracy and Irene Dunne that jump started his career. My favorite Johnson roles are: the ever resourceful and knowing Tech. Sgt in Command Decision (1948) with Clark Gable and Walter Pidgeon; the sardonic pal of Gene Kelly in Brigadoon (1954); and in the same year, the earnest, not quite that bright but capable Lt. Maryk in Caine Mutiny. He really was a good actor, but just never got the credit for it.
I remember him fondly from his appearances on The Tonight Show. Always entertaining, wearing that big smile, sometimes a tad tipsy with a drink in hand, and wearing those red socks ... always.