Born on February 4, 1928, Ketchum began his entertainment career as a stand-up comic before transitioning to acting. He was a series regular in two short-lived sitcoms — I’m Dickens, He’s Fenster (1962—63) and Camp Runamuck (1965—66) — before landing his most iconic role.
From 1966 to 1967, Ketchum appeared on the hit spy spoof Get Smart as Agent 13, the hapless undercover operative who always found himself hidden in the most inconvenient places — from vending machines to mailboxes — when receiving orders from Maxwell Smart (Don Adams). Though his appearances were brief, his deadpan delivery and perfectly pitched frustration made the character a fan favorite.