In the first episode of I Love Lucy, somebody said “Why don’t we have a cigarette?” The result looked like this:
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They took the cigarettes out of a wooden box and never identified the brand, so the show wasn’t cashing in on a product placement. It was just a general pro-smoking message! Worse yet, Lucille Ball was obviously very pregnant (in real life) while she puffed away. She wore robes and aprons to hide it because her character was not pregnant, but it was painfully obvious whenever her contour could be seen. (Note how in the scene above she was in a very odd outfit for wandering around the apartment.)
Later in the episode, there was an obvious product placement. Fred and Ricky each drank a bottle of Ruppert beer on camera, and when they set the bottles down, the labels were conveniently turned toward the camera and in focus.