It's Halloween I'm Turning Green!

Used paperback. Great for ages 6-10. 

It's Halloween, I'm Turning Green! is a funny holiday-themed entry in the My Weird School Special Series by Dan Gutman. A.J. and his Ella Mentry School friends go trick-or-treating, encounter a mysterious "Halloween Monster" who steals their candy, and deal with a stomachache after eating too much chocolate.