Random Swapper

"I wish I had a small device that allows me to randomly swap one specific thing between two people." After Jon said that, an odd-looking gun appeared on his bed. It looked like something out of an old sci-fi movie. He picked it up and looked at it. "So what kind of swapper is it?" Karyn asked. "The swap is random. So who knows? Maybe it will swap two people's heads, or maybe it'll swap two people's genders, or maybe their minds. Like I said, it's totally random. So, who should we use it on first?" Jon asked.