C.J.

"A young genius has invented a ray gun that shrinks anything it touches – including you! But when the scientist and her invention go missing, you'll have to keep the shrink ray from falling into the wrong hands, and find a way to stop the thief and find a way to grow back to normal size."

C.J. is a genius and a student of the River City local school P.S 201.

Science fair theft
C.J. was one of Mr. Silva's students, and she won every science fair he ever held at the school. She became very popular and Mr. Silva realized he could get that kind of popularity (and money) if he stole one of her inventions. So he swiped the Shrink Ray she was planning on unveiling at the science fair and used it to shrink her down and kept her in his office to keep her quiet. She was able to contact a Poptropican who had also been shrunk through morse code and a telescope. She told the Poptropican that Mr. Silva was the thief. The Poptropican rushed to go find her, but Mr. Silva tried to shrink them down to an impossibly small size, which would probably destroy them. But the shrink ray bounced off of a mirror and hit him, which shrunk him down and caused him to fall into a jar of ants. The Poptropican and CJ reversed the gun and shot themselves to return to normal size and CJ used Mr. Silva as her science fair project, "The Incredible Shrunken Man." (Shrink Ray Island).

Trivia

 * She was mentioned to have won three other science fairs.