(The first part of this is Hikaru's but with a different result.)
"You're my bisexual girlfriend," Jon blurted out at Sarah's father, thinking it would do something.
Jon was still new using the stone, and had run across one of the stranger traits of the stone. If you don't tell the stone how to do something, it might not get specific.
For instance, if you say "I wish I could fly to the store", that doesn't mean you get wings that let you fly to the store and no place else. Instead, it makes you able to fly to the store by making you able to fly anywhere. If you can fly anywhere, then you can fly to the store, so the wish did indeed come true--having the general version become true is a way for the specific version to be true.
Jon didn't add "...and nobody else", so the simplest way for the stone to give Jon the ability to make a female into his bisexual girlfriend was to give him the ability to make anyone into one.
Mr. McMillan immediately paused, then grew breasts and became a female version of himself. S/he looked at Jon with lust...
Jon almost expected Sarah to vanish, since he had just turned both her parents into his girlfriends. However, she remained.
Then, it occurred to Jon that his wish had specified that reality would change so that Sarah was his bisexual girlfriend until he released her. If she did not exist, she could not possibly be his girlfriend. So, the wish had allowed her to stay. Jon wondered what would happen if he ended the relationship right there. Would she blink out of existence? Or would she simply be given another slot to fill in reality? Did he really want to find out?
These inner questions were interrupted by a pair of arms wrapping around him. It was the former Mr. McMillan, now shirtless like Susan. "Oh, Jon," she purred. "Susan and I are so happy you've called us all here. Now we can have some fun together."
"M-Mister I mean, Mrs " Jon stammered, realizing he had no idea what to call her now.
His latest girlfriend blinked at him before giggling. "Why so formal, Jon? You know my name. It's just me, Brianna."
Jon gulped. "Um, right."
