He played Jamie, a teenager adopted by the Cartrights to give Ben someone to offer fatherly advice to (and, apparently, to give Michael Landon some competition in the bulge department).
But before he blossomed into teenage biceps and bulges, Mitch was a popular child star, with roles in Adam-12, Ironside, The Young Rebels, and The Immortal.
He was best known for The Reivers (1969), set in turn of the century Mississippi, as an 11-year old who tags along with his free-spirit relative (Steve McQueen) on a trip to a brothel in Memphis, sees naked ladies, and "comes of age" (although he doesn't actually have sex with anyone).
In Two Boys (1970), Jud (Mitch) and his boyfriend Billy (Mark Kearney) "come of age" in a small Midwestern town.
In The Boy from Dead Man's Bayou (1971), Jeannot (Mitch) and Claude (Michael Lookinland from The Brady Bunch) buddy-bond as they wrest a church bell from the jaws of a giant alligator.
His characters got girls on Little House on the Prairie (1975) and State Fair (1976), and were backwoods outsiders who didn't get anyone on Here Come the Brides and Saturday morning's The Mighty Isis (1975) and Ark II (1976).
Today Mitch lives in Southern California, where he is active in directing, music, and church groups.
But gay Boomers will always remember him for the bulge and biceps of Bonanza.