Factual error: An old man appears with children following him. This is supposed to be pedagogue Janusz Korczak. It appeared as if he was just wearing a suit and a Jewish arm band. In the Warsaw Ghetto, Mr. Korczak never wore an arm band and wore his WWI Polish Army Uniform, both as acts of defiance. He was beaten and almost put to death (he had connections) for not wearing an arm band so having one on in the movie is inaccurate.
Factual error: After Berry and one of the Country Bears get in the bus to find the others, they show a scene with the bus going along a road and Berry leans out the window. Here you can see the side of the bus is spick 'n' span clean. Then, later, the bus is as dirty as it was when it left the shack, very noticeable at the start of the carwash scene.
Factual error: Although the tie is obviously done for the purpose of the story, the fact is that Morris Brown would never be given high marks for their performance at the Big Southern Classic. This is a marching band competition, and they do little moving at all, let alone actually marching, changes of formation, etc. If anything they would rank last of all schools, if they weren't disqualified outright.
Factual error: DJ Iz mentions how Detroit never tears down any of its abandoned buildings and just builds casinos. No casinos were built in Detroit until 1997-98, and the film is supposed to be set in 1995.
Factual error: Whenever Steve Coogan is driving his old brown car during the 70s and 80s, you can look out of his windows and see cars that weren't made then, even some with current registration plates on, either driving past, or parked up in driveways, or on the side of the road.