Most of his work at Warner Brothers was limited to light comedy work with Morgan, and later Doris Day (who in her autobiography would credit Carson as one of her early Hollywood mentors). Critics generally agree that Carson's best work was in "Mildred Pierce" (1945), where he played the perpetually scheming Wally Fay opposite Joan Crawford in the title role. Also in 1945, he played the role of Harold Pierson, the second husband of Louise Randall, played by Rosalind Russell, in "Roughly Speaking". Another role which won accolades for him was as publicist Matt Libby in "A Star is Born" (1954). One of his last film roles was as the older brother "Gooper" in "Cat on a Hot Tin Roof" (1958).