The supercomputer known as Watson managed to destroy Jeopardy! superstars during the second round of play, but had no clue that Toronto was not a U.S. city.
Flesh-and-blood contestant Brad Rutter entered the second day of the three-day competition tied with Watson while fellow air-breathing contestant Ken Jennings was only a few thousand dollars behind giving some hope to humankind.
But on Day 2, the computer took off, buzzing in first almost all the time opening a massive lead of more than $30,000 going into Final Jeopardy! But that was when Watson finally stumbled.
The category: U.S. cities.
The question: "This U.S. city's largest airport is named for a famous World War II hero, its second largest for a famous World War II battle."
All-time Jeopardy! money winner Rutter and 74-game winner Jennings both answered correctly with Chicago, but Watson wrote down: "What is Toronto???" as the audience gasped.
Host Alex Trebek, a native of Sudbury, Ont., read the answer slowly as if he was asking a question. Trebek and many others seemed to be in disbelief.
While Toronto's smaller airport is named after Billy Bishop, a First World War flying ace, the larger one is named after late prime minister Lester B. Pearson. This is a small detail compared to the obvious fact Toronto is not a U.S. city.
But Watson easily answered a question about 'Saturday Night Live'.
In fairness to Watson, there are a number of cities in the U.S. named Toronto. They are in Kansas (population 312), Ohio (population 5,676) and South Dakota (population 202), but none have an airport.
Representatives from IBM, who created Watson, did not immediately return phone calls, so it is not known how the machine malfunctioned.
The winner will be crowned after the final round Wednesday night.