Oh no - do you know for sure he's been allowed to see these things and isn't just quoting other children? I think a chat with parents is essential, there's only so much you can do if his obsessions are being reinforced by him still seeing these films at home. If they aren't aware of how inappropriate these films are and the affect that they have on their son, then they need to be told very clearly! My son has autism and we had problems when he was in Y3 - he wasn't allowed to watch inappropriate things but his best friend was and told him all about them which was difficult to manage. Even with support from home this might take a while to stop as obsessions are by their nature difficult to change. Continuing with other more appropriate themes is worth a try, if Pokemon or Harry Potter don't catch his attention try another theme - Star Wars is a popular one with lots of areas just perfect for obsession! Social stories about playtime and appropriate play might help. Or finding out what interests another child - a child who the boy with autism admires - and trying to steer him that way. If my son really liked someone he would begin to develop an interest in the things they liked (within reason, he was never going to play football!) It's likely to be a long journery with no quick fixes!