Who is 4?
I really need to address this issue in our home. My 5 year old is often on Youtube, which I monitor by peeking in periodically from the other room (not the safest system). He usually watches other kids reviewing Lego sets, or stop-motion videos kids have made using Legos. Furthermore, my 21 month old just figured out how to click the pictures to get to more Youtube videos this morning! She watches baby and animal slideshows.