In the movie, What's Eating Gilbert Grape, Gilbert's younger brother Arnie has a metal disability. Arnie is mentally challenged and requires constant supervision. He will take off and run and climb up the water tower if he is not being watched every minute. He sees no harm in doing this and usually has to be convinced to climb down. Once Gilbert had to sing to him over the loudspeaker a simple little song that he was use to hearing to get him down. He doesn't understand that his actions have consequences. He believes what he is told and can't grasp some simple concepts such as the difference between goodnight and goodbye. He is repetitive in some things he say and will just repeat what is said to him without even understanding what it is. Once at the dinner table he kept hollering over and over that, "Dad is dead!" not realizing what he was saying or how it was affecting the others.
He doesn't forget a lot of things though. Once Gilbert left him in the bathtub over night and Arnie didn't know to just get out of the tub. He sat in the water all night until he was found the next morning. After that Arnie was scared of the water and wouldn't go in it willingly for nothing. He liked to play games with Gilbert though. They would play hide and seek with Arnie being the one hid. Gilbert would pretend to be looking for him and Arnie would get a big kick out of it.
The act that was put on portraying Arnie in this movie was a good one. He did things you would think a mentally challenged child would do. He even had the movements of flicking his finger at his nose down pat, and this action was very repetitive. The kids in the community would make fun of him, call him names, and just push him around.
What's Eating Gilbert Grape The Movie