I have been slowly stealing my boyfriends socks so he has more and more odd pairs.
What's the reasoning for wanting your boyfriend to have an odd pair of socks?
I like the fact that he would look like a mess when he is out of house
I can understand you want to have a little fun and prank your boyfriend. Stealing from him isn't the way ago about doing that, you should try to find other things to do to your boyfriend that would not involve stealing from him and inherently hurting him.
I know but I believe he'll find ways to have fun with that.
If you continue to steal his socks he may find out and be very upset with you. It seems like a harmless enough prank, but think of how frustrating it can get to not find a pair of socks. Return his socks and find a more harmless way to tease him.