So, if your dad works, or when he's out one night sneak into his closet and take all of his work pants. Be sure to fill his closet with other things like jeans or sweats: he wont notice, and hide the pants some where like the basement or attic. I did this to my dad, it was so funny. Just be sure to have a camera around to snap some pics to get proof of the confusion.
On another day I sneaked into the bathroom while he was in the shower and took all his clothes and all the towels while he had his eyes closed and busy washing his hair. He kept on calling for us and we all kept quiet. He got really mad because nobody heard him. When he eventually decided to come out we were all standing laughing around the corner.