A Chet Gecko #1 Mystery The Chameleon Wore Chartreuse by Bruce Hale

My third grader found this series at our library and is thoroughly enjoying them.
He says these books are funny and exciting.
For this case, Chet is suppose to find a missing chameleon, Billy.  His sister Shirley promised Chet a stinkbug pie if he finds Billy.
As I skimmed the book, I saw the words "brat" and other name calling.
Guided Reading Level: O (end of 3rd grade)
Grade Level Equivalent: 3.7