Factual error: In episode 17 there are some scenes showing sick 4400s all around the world. One of them is being carried into an ambulance car in Frankfurt, Germany. The ambulance car's number plate begins with the letters FM meaning Frankfurt am Main. The correct abbreviation for Frankfurt am Main on German number plates is F - not FM.

Factual error: In the pilot episode, when Lily and Richard are talking in a coffee shop, a TransLink trolley passes by outside. A TransLink is never seen in Seattle, but it is seen in Vancouver, where the show is filmed.