"You're not my bisexual girlfriend," Jon said to Sarah. In a blink of an eye, Sarah was clothed again and staring at Jon, looking very shocked.
"What are you doing in my bedroom, you pervert?!"
Jon wasn't sure what to say. He thought that it would change reality so that Jon was back home or something, not still at Sarah's house. But then he thought that maybe that was because changing reality didn't change him, only Sarah.
"I'm calling the cops!"
"Wait, wait," Jon said. He had to fix this. "You're my bisexual girlfriend."
Just as suddenly as her last change was, Sarah went from being fully dressed to being fully naked. She walked over to him and rubbed up against him, letting him get a feel. "Come on, Jon. Get undressed. I want some sex," she purred.
It was like the last minute never happened. At least Jon found out that his "magic phrases" worked the way he wished them to.