Factual error: Will's hospital chart states he is taking Warfarin and Coumadin. These are both the same drug to prevent blood clots. He would not be on both. (00:31:50)
Factual error: When J.J. first discovers his powers and understands math, the parabola "seen" on the board is wrong for the given equation and it's different than what J.J. actually ends up drawing, which seems more like the right answer.
Factual error: The show is supposed to be taking place in NYC, however its clear by the shooting locations that its shot in Toronto. This can also be seen very by the various signs throughout the city that are not found in the US and are very Canadian in nature, such as the Do Not Enter and One Way.