Factual error: In Season 2, Episode 3, Peter and the Irish family rob the bookmakers and the security guards shoot at them. In Ireland, even the police don't carry weapons. Let alone security guards.
Factual error: The solar eclipses in the show that affected the characters' powers were referred to several times as "global events". In the episode with the second eclipse it's shown to be visible in locations thousands of kilometers away from each other at the same time. This is simply impossible, since a solar eclipse occurs when the moon passes between the Earth and the sun, casting a moving shadow that can be only about 250 km in diameter (for a total eclipse). The partial eclipse can be viewed in a much wider region, but the eclipse in the show was a total one. It's not a global event, but a local one.
Factual error: When Nathan goes to Cork to find his brother, he gets out of a black cab with a yellow license plate, both of which are characteristic of ENGLISH taxis, not Irish ones.
Factual error: During Hiro's journey around New York, a Carl's Jr. restaurant is visible in the background. That restaurant isn't called "Carl's Jr." on the East coast; it's called "Hardee's."
(Volume Two: Generations) Four Months Later... - S2-E1
Factual error: In the scene where Hiro is in ancient Japan posing as Takezo Kensei to rescue the girl, what looks like a Gatorade bottle can be seen in the grass as they ride away. (00:18:45)
One of Us, One of Them - S3-E3
Factual error: When Hiro and Ando stand in front of a cinema in Berlin, Germany, you can see three movies posters in the background announcing a Buster Keaton festival. The left one shows his movie 'Cops' - but the German title 'Politzisten' is wrong - it should be 'Polizisten'. (00:09:55)
Chosen answer: It's not been made 100% clear. It was originally assumed that he actually consumed part of the brain, but this has turned out not to be the case. Sylar has been shown all along to have an instinctive knowledge of how things work and how to fix them - this is his actual original power and the ability that made him an exceptional watchmaker and repairer. It appears that he uses a similar process when acquiring new powers - he exposes the brain of the target, allowing him to examine it and determine how their power functions. He can then apply that knowledge to his own brain, allowing him to replicate the ability in question.
Tailkinker ★