Melvin and Howard (1980)

This movie tells the possibly true story of Melvin Dummar. Melvin is a nice guy, but he is a total loser: unlucky, impractical and can't keep a job. One night, however, he helps an old man who has had a motorcycle accident in the desert. Melvin laughs when the old man says he is Howard Hughes, the eccentric multimillionaire. But when Howard Hughes dies, Melvin is mailed a will leaving him part of the estate!