I'm planning to stay at home for the day to raid my mother's room.
That doesn't sound good. Why do you want to raid your mom's room?
(1) My mother is not that nice to me, (2) I like to play cruel jokes on my mom and (3) Whatever I do to her will always be returned to me threefold.
Going through your mom's bedroom and personal items isn't okay. Playing pranks and joking with family is one thing, but being cruel and knowing that she'll punish you is leading towards a troubled future. Have you talked to someone about what you do?
I just made a joke.
Well it's not nice to go through her stuff without her permission. You should just leave her stuff alone.