Try the invisibility vial.

Francis looked closely at the vial with invisibility written on it. In smaller writing the instructions said that one level teaspoon would provide invisibility for twelve hours.

"Neat, but it's gotta be a gag." Francis said to himself.

Still it couldn't hurt to try, could it? Francis went down to his kitchen and there unstoppered the vial. It smelt sweet. He measured out a teaspoonful and drank it. His body began to tingle and he held his hands up to observe what was happening. His skin slowly took on a silvery hue. Then as he stared his hands began to fade to transparency till they were totally invisible.

Francis ran to the full length mirror in the hall. All that could be seen in the mirror was his clothes standing up, apparently on their own. Francis stripped and looked again, nothing! He felt himself, slapping his chest, arms and legs. He was still solid enough.

"Boy, can I have some fun with this." Francis said.

He took a quick look at the clock and noted the time. Thinking carefully he took his key and slipped out the back door and hid the key in the backyard, so he could get back in later.

Francis strolled down the street, he found he had to concentrate more on his surroundings as the people walking about came straight at him and he had to keep dodging to avoid having them walk into him. Luckily it was summer so being nude wasn't a problem. The thought that he was walking amongst these people stark bollock naked without them knowing gave Francis a thrill. His cock began to stiffen as the possibilities began to dawn on him.

"Hmmm, where should I go first?" Francis mused.