The wonders of make-up and being 6'3: Between Richie, Potsie, Ralph and older brother Chuck, Gavan O'Herlihy is the youngest of the four. Yet the viewer never suspects. Nor does the ordinary viewer notice that O'Herlihy is playing the part of a Milwaukee-raised oldest son with a natural Irish brogue.
O'Herlihy comes from a show business family. His father and uncle, two of his four siblings plus his brother's wife, and a niece and a nephew have all been involved in TV or movies - all credited under the name of O'Herlihy.
O'Herlihy has more film credits than most would estimate, over 30 different movies. In contrast to the low-key Chuck Cunningham role, O'Herlihy plays predominantly villain roles, such as Airk Thaughbaer in Willow, or Brad in Superman III. Many of his movies were directed by TV brother Ron Howard.