When I was about 3 my sister (then aged about 9) decided she was leaving home. She went to her room and packed a bag full of toys. When Mum asked her what she was doing she simply told her she was leaving home, Mum said OK (knowing it wouldn't last). My sister then added "And I'm taking Jenny with me". Again Mum said OK. With that my Sister took my hand and left, we walked around the block and then went home again. My Sister obviously realised she would miss dinner.
That was my first experience of leaving home.