The Jerk (1979)

"A rags to riches to rags story."

After discovering he's not really black like the rest of his family, likable dimwit Navin Johnson sets off on a hilarious misadventure that takes him from rags to riches and back again. The slaphappy jerk strikes it rich, but life in the fast lane isn't all it's cracked up to be and, in the end, all that really matters to Johnson is his true love.