"A simple rule of robotic personality seems to be: don’t make things the most efficient way," said Magnus Wurzer, who has been running the Vienna-based Roboexotica, a festival where scientists have gone to build, showcase and discuss "cocktail robots" since 1999.

One entry, Beerbot, detects approaching people and asks for beer money. When it acquires enough, it "buys" itself a beer. Bystanders can watch it flow into a transparent bladder. As for other humanizing behaviors, "like a robot that doesn’t stop short at lighting a cigarette but actually goes ahead and smokes it?" Mr. Wurzer says, "We had that.

Roboexotica has inspired a stateside version as well, which just had its third annual celebration in San Francisco.

And in at least one case in Europe, a robot actually got behind a bar. From 1999 to 2002, a scarlet-eyed metal robot named Cynthia poured drinks at Cynthia's Bridge Bar and Lounge in London. But according to Mr. Wurzer, "she was too costly to maintain once the bar was sold by the robot's maker."