Ron is 12 years old. He is the younger son of Russ and Mae Thompson and younger brother of Russ Jr. He was shrunken by accident once and had a big adventure with his brother and neighbors Nick and Amy Szalinski. He and the others were eventually returned to their normal size.
Ron is rude, arrogant, worrisome and selfish and can be blunt at times. He enjoys fishing and baseball. He is also a bully near Nick, but during their adventure, he warms towards him and finally becomes his friend. He is tough, but when the ant he befriended died after being stung by a scorpion, he broke down and sobbed.