For Robie was the logical conclusion of the development of vending machines. All the earlier ones had stood in one place, on a floor or hanging on a wall, and blankly delivered merchandise in return for coins, whereas Robie searched for customers. He was the demonstration model of a line of sales robots to be manufactured by Shuler Vending Machines, provided the public invested enough in stocks to give the company capital to go into mass production.
Robie radared the crowd, found that it surrounded him solidly, and stopped. With a carefully built-in sense of timing, he waited for the tension and expectation to mount before he began talking.

(Robie from 'A Bad Day for Sales' by Fritz Leiber)

The lower part of Robie's body was a metal hemisphere hemmed with sponge rubber and not quite touching the sidewalk. The upper was a metal box with black holes in it. The box could swivel and duck.
A chromium-bright hoopskirt with a turret on top.
"Reminds me too much of the Little Joe Paratanks," a legless veteran of the Persian War muttered, and rapidly rolled himself away on wheels rather like Robie's...
Robie glided very slowly down the path, deftly jogging aside whenever he got too close to ankles in skylon or sockassins. The rubber buffer on his hoopskirt was merely an added safeguard...
"Hello, youngster," Robie said in a voice that was smooth as that of a TV star, and was, in fact, a recording of one... A metal arm shot down from his neck, stopped just short of the boy...
"For you," Robie said.
The boy gingerly took the red polly-lop from the neatly fashioned blunt metal claws, and began to unwrap it.
"Nothing to say?" asked Robie.
"Uh—thank you."
After a suitable pause, Robie continued. "And how about a nice refreshing drink of Poppy Pop to go with your polly-lop?" The boy lifted his eyes, but didn't stop licking the candy. Robie waggled his claws slightly. "Just give me a quarter and within five seconds—"