i think most of the adult stuff just washes over their heads.
My DSD (6) was watching "2 1/2 men" the other day. She found it on the sky+ box and seemed to be enjoying it when i walked in. The sexual references just shot over her head thankfully but it made me squirm waiting for questions i was sure were to follow. They didnt follow. She just thought the jokes she didnt get were grown up jokes and that was that. unnatural child.