The copyright which exists in all kinds of "publications" ranging from books to videos to film to TV programmes is easy to infringe, as the Guru says.
If you take a look at the User Video thread contributed by "Rollingstock", there's a fascinating example. He doesn't think he'd doing anything wrong, but back in the days when dear old Britt Allcroft owned the TtheTE rights, she'd have had his kidneys on a plate!
If the current rights owners, Hit Entertainment, fancied him, they could certainly take a very large bite out of him . . . but their target kid market won't see this until they're out of the age range, so they wouldn't bother. If he got a broadcast showing it would be very different!
I try to make someone happy every day - but it may not be your turn today . . .