Revealing mistake: The waterfront set always features a blue, cloud-dotted sky, even when the streets are wet from supposed rain. And the clouds are static, never moving or changing, betraying the fact that they're part of a backdrop.
Barbary Coast (1975)
1 revealing mistake in show generally - chronological order
Starring: William Shatner, Richard Kiel, Doug McClure, Dave Turner
Visible crew/equipment: When Cable closes the cabinet, the boom shadow can be seen moving on the wall behind him. (00:04:20)