What TV show which has been running off and on since the 1950s was most memorably hosted by Allen Funt?

The TV show you're referring to is "Candid Camera." Initially launched in the 1940s, it became widely popular in the 1950s under the hosting of Allen Funt, who introduced hidden camera pranks to entertain viewers by capturing people's reactions to humorous situations. The show's format has allowed it to return in various iterations over the decades.