If you happen to hear something similar to "yo ho ho and a bottle of rum" coming from inside your child's room, don't panic, he is just pretending to be a pirate.
Pretend play is probably one of their favorite activities and more than likely it is the same for the parents or caregivers because it gives you an inside peek at the fascinating mind of a child. Imagination rules a child's playtime which is great and should be encouraged while they are young because the real world comes far too quickly in their life.
It's not uncommon to hear someone tell a child to grow up and while, yes it is a necessary step in their development it should not come too soon. Nor should it happen all at once. It should be a gradual process, helping them to adjust to this new world of reality and responsibility. This can be accomplished in any number of ways, perhaps beginning with small age (and size) appropriate chores or jobs.
Do not get frustrated when he seems like he comprehends everything you are trying to teach one day and the next its back to what? This is very normal and expected since their attention span is often very short for a number of years. Just be patient, he will eventually understand what is expected of him and will also begin to learn why these lessons are important.