William Schallert, a familiar presence on prime-time television for decades, notably as the long-suffering father and uncle to the “identical cousins” played by Patty Duke on the hit 1960s sitcom “The Patty Duke Show,” died on Sunday in Pacific Palisades, Calif. He was 93.

His son Edwin confirmed the death.

Mr. Schallert’s career spanned generations and genres. Over more than 60 years he racked up scores of credits in episodic television as well as noteworthy performances in motion pictures, on the Off Broadway stage and as a voice-over artist.

With his preternaturally mature, intelligent but (by Hollywood standards) unremarkable looks, he was cast almost from the beginning as an authority figure — a father or a teacher, a doctor or a scientist, a mayor or a judge. Most active from the 1950s through the ’80s, Mr. Schallert remained seemingly unchanged in appearance and persona over time, and he was still working in his 90s, dismissing any thoughts of retirement.

On television it sometimes seemed as if he was everywhere. A versatile character actor with a comforting presence, he was equally at home in comedies and dramas, with a résumé ranging from “Leave It to Beaver,” “The Twilight Zone,” “Dr. Kildare” and “The Wild Wild West” to “Melrose Place,” “True Blood” and “Desperate Housewives.”