In the film, Michael wants to be an only child (like in the book, he is an ordinary child, unlike Matilda). Michael's nickname for Matilda is "Dip Face."
In the book, Michael leaves his little sister alone and at the end, he waves goodbye to Matilda. In the film, Zinnia is the one who waves goodbye and says "ciao" while smiling as he stares dumbly at her.
In both the film and book, he was educated by his father as he is to inherit the used car dealing business in the future; however, in the film, Harry was more into showing Michael some details and he developed an interest and fascination in the business.
Michael bullies Matilda and his nickname for her is "Dip Face." He wants to be an only child. Matilda also has telekinetic powers and superhuman intelligence, unlike her brother. Michael also throws marshmallows at Matilda