In the book, Michael leaves his little sister alone and waves goodbye to her at the end.
In the film, Zinnia is the only one who waves goodbye and says 'ciao while smiling as he stares dumbly at her.
In the film, Michael wants to be the only child in the family (like in the book, he is an ordinary child, unlike Matilda). Michael's nickname for Matilda is Dip Face.
Film and Book
In both the film and the 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 unto showing Michael some details and he developed an interest and fascination in the business.
In the 1996 film adaptation and the musical, Michael is lazy and doesn't even pay attention to Matilda
When he was in his car seat he uses his toy to play with. When he is older, he threw marshmallows at Matilda, while calling her Dip face.
Later in the movie, hey says Hey, Dip face, have a carrot and used a spoon to throw the carrot directly at Matilda, but she turns around and makes it stop right in front of her, causing him to look shocked. Matilda then makes the carrot turn around and zoom back over to Michael, who drops the spoon the counter right before the carrot enters his mouth. Matilda laughs a little as Michael then begins coughing; Harry then calls, Chew your food! You're an animal!
In the book, he is an ordinary boy, but a messy eater. He likes mostly peanut butter and jam sandwiches which he makes haphazardly and messily eats the resulting mess. He doesn't interact with Matilda.
In the 1996 film, 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 who also throws marshmallows and a carrot at Matilda.