Regina finds out that Kälteen Bars is designed for weight-gain.
Copyright : PARAMOUNT
PS: [SPOILERS / Explanation] Why Regina put her own picture in the "burn book" instead of Cady Heron?
So she can report the book to the school's headmaster. It's a smart way to create her own alibi that she doesn't write those mean comments. This way, Regina George can blame it on her friends, Cady (to be specific), Gretchen and Karen, because their names ain't in the burn book.
