Almost every thing contains elements of fiction if you think about it...because even when someone writes something to be factual they almost inevitably incorporate bias or errors based on their view point or understanding of the subject.
That said, fiction with a good story line that pulls elements of reality into it in a believable way (ie setting, time of setting, maybe some historical scenario that plays a part in the story, laws of physics) can be really awesome, but so can something that seems to have no sane connections to reality like FLCL.