Harold "Harry" Wormwood is the father of Michael and Matilda Wormwood and the husband of Zinnia Wormwood. In the movie Matilda, he's played by Danny DeVito (who also directed the film, and did the film's narration).
Harry was a used car salesman who ran Wormwood Motors, which sold used cars for more than what they were worth (especially since they were defunct and quite broken) while also dealing in stolen car parts.
He is the husband of Zinnia Wormwood, with whom he had two children, Michael and Matilda. Although he treated his son Michael quite well, he was rather rude and dismissive towards his daughter Matilda, whom he described as a "mistake".
After returning from work having made a lot of money, he had Michael add up the total of his profits from selling the cars Harry had sold. Matilda was able to correctly get the right answer, though Harry just accused her of cheating and claimed that she could see the paper Michael was working out the total on (despite it being at a distance that Matilda couldn't have been able to see it) and accused Matilda of being smart with him and said "when a person is bad, that person has to be taught a lesson".
Unknown to him, Harry had given Matilda the first piece of practical advice she could use; although he said 'person', he meant to say 'child' and introduced the idea that children could punish their parents. The next day, Matilda bleached Harry's hair (giving it a blonde look) and after he took her and Michael to work that day, she got payback against him after he talked down on her by gluing his hat to his head.
One of his customers at his car dealership was Agatha Trunchbull, the headmistress (principal) of Crunchem Hall. After he sold her a used car, he arranged to have his daughter attend Crunchem Hall.
Later, when Miss Trunchbull was driving the car she bought from Wormwood, it broke down, with the engine falling out onto the road (in the book). It was then that Trunchbull discovered that she had been cheated, and in the film, she called Wormwood on the phone, making threats while taking her anger on Matilda and locked her in the Chokey (a prison cell in her office).
Throughout the film, Wormwood's house was frequented by FBI agents. Near the end, after his scheme was busted, he fled the country with his wife and son. The family fled to Spain in the book, and to Guam in the film. Rather begrudgingly, he and Zinnia decided to sign the adoption papers to allow Matilda's teacher Miss Honey to take care of Matilda (the first time he and Zinnia had done anything good for Matilda). He was not seen again afterwards, and was presumably arrested and charged with his crimes.
Unlike most parents, Harry Wormwood is shown to be greedy, selfish, dishonest, arrogant and bad-tempered. Also, he frequently abused his daughter Matilda by calling her names and tearing her books apart, as well as being dismissive. In addition, he did not appreciate his daughter's thirst for knowledge and her precocious gifts, instead scoffing at the idea of education, which deeply offended Matilda's teacher Miss Honey. When his daughter, Matilda, tried to warn him about his illegal dealings, he rudely shut her down and called her names.
He had a good relationship with his wife and son, but not his daughter, which ultimately resulted in the breakdown of the family, as Matilda refused to join them when the family fled the country to avoid the authorities. His dishonesty, arrogance and selfishness led to his downfall, costing him his home, his business and his money. His exact fate is unknown, although he was likely caught and arrested for his illegal dealings, and sentenced to prison.