Fred Mertz was a priceless character: the next-door neighbor, close friend, and penny-pinching landlord of Lucy and Ricky Ricardo. Frawley had to fight for the part. Originally, Lucille Ball had wanted Gale Gordon for the role, but Gordon was unavailable. Frawley got the role only after convincing network executives that he wouldn't let his alcohol problem interfere with his work. During his time on "I Love Lucy," Frawley made no bones about his dislike for his on-screen wife, Vivian Vance. He once remarked: "She's one of the finest gals to come out of Kansas, but I often wish she'd go back there." Likewise, Vance was often vocal with her disgust about having an on screen husband who was old enough to be her father.

William Frawley was born in Burlington, Iowa. As a boy he sang at St. Pauls' Catholic Church and played at the Burlington Opera House. His first job was as a stenographer for the Union Pacific Railroad. He did vaudeville with his brother Paul, then joined pianist Franz Rath in an act they took to San Francisco. After four years, in 1914 he formed a light comedy act with his new wife Edna Louise Broedt, "Frawley and Louise," touring the Orpheum and Keith circuits until they divorced in 1927.

He next moved to Broadway and then, in 1932, to Hollywood with Paramount. By 1951, when he contacted Lucille Ball about a part in her TV show, I Love Lucy, he had performed in over 100 films.

During his "I Love Lucy" years, Frawley found time for occasional guest appearances on other shows such as "The Mickey Mouse Club," "The Gale Storm Show," "The Red Skelton Show," "The Loretta Young Show," and "Shower of Stars." His Fred Mertz role lasted until the show ended in 1960. Then, in 1960, he began work on another long-running series, "My Three Sons." On that show, he played Michael Francis "Bub" O'Casey, father-in-law to Fred MacMurray's character and housekeeper for the family of men.

In 1964, Frawley became too ill to work and at the end of the season was replaced on "My Three Sons" by William Demarest .

Frawley's last television appearance was a cameo on a 1965 episode of "The Lucy Show," entitled "Lucy and the Countess Have a Horse Guest." In that episode, Lucy Carmichael commented on how familiar he seemed to her.

He collapsed of a heart attack on March 3, 1966, aged seventy-nine, walking along Hollywood Boulevard after seeing a movie. He is buried in San Fernando Mission Cemetary.