It still remains unknown to me.
Last year, my family and I used to live in a villa in Sydney. I have had this experience 3 times. The weird thing was that "the unknown" used to live in my older sisters room but surprisingly did no harm to her.
The first experience was, one night my sister could not sleep and so (she normally did this), she put on her I-pod and that way she would fall asleep. However, when she went to turn her I-pod on it did not turn on as it said "re-charge battery low" and within seconds it switched off - it was flat. She placed her I-pod in her bag and tried to sleep.
At 2:04am, my sister woke up hearing the sound of music playing. When my sister was awake, she could hear the song "Disturbia - Rihanna" blasting from her headphones. Typical aye? DISTURBIA. The weird thing was how does an I-pod Nano turn on by itself, without someone touching the button? AND WHEN IT IS FLAT.
The second experience was when my dad was asleep and I was studying. I was disturbed, when I heard someone in my sisters room flicking sheets very aggressively. I did not know who or what was it but I was too afraid to go in her room and check. It was like someone just continuously throwing sheets on the study table. I turned on my music and ignored it.
The last experience was with my sister again. She was studying for her Uni exams, and at 2:08am, she heard footsteps approaching her room (we have a hallway and you can hear when someone walks as the tiles and walls allow very good sound to come through). The footsteps got faster and louder and as soon as they reached my sisters room they stopped.
This happened again the next night. This time my sister got really scared and screamed "mum is that you?!" and the footsteps just stopped. My mum woke up and responded saying she was asleep. Once again she was disturbed.
I live in a different house now but that will always be a notion I will ponder over. It has disturbed me for life!