I found a Choose Your Own Change branch with IB extravaganza!
It all starts here:
http://www.cyoc.net/stories/chapter_...apter_id=13184
15-yearold boy unknowingly receives a witch's wish-granting magical powers.
Here are the IB threads I've found so far:
http://www.cyoc.net/stories/chapter_...lay_previous=1
He absentmindedly wishes that a overweight girl he knows was better-looking.
http://www.cyoc.net/stories/chapter_...lay_previous=1
...or he gives himself a variety of superpowers, secretly visits a girl he likes and casts an IB blessing on her underwear.
http://www.cyoc.net/stories/chapter_...lay_previous=1
...or secretly wishes his sister into an improved version of herself.
http://www.cyoc.net/stories/chapter_...lay_previous=1
...or lures a girl to enter a Faust-like pact to become hotter...
http://www.cyoc.net/stories/chapter_...lay_previous=1
...or his sister tricks him into giving him the power, and after turning him into her identical twin she decides to wish for some improvements to them both.
http://www.cyoc.net/stories/chapter_...apter_id=13186
...or even better, the powers went to his sister to begin with, who absentmindedly wishes herself to gradually become gorgeous. And then she does it to her friend, too...