Dickie Jones as cub pilot Sam Clemens and Robert Barrat as Horace Bixby in the The Adventures of Mark Twain (1944). The kid is 13 years old but Clemens was actually 22 years old when he met Bixby and discussed learning the river under him. The movie perpetuated the myth that Clemens went straight from Hannibal into the river trade but he was actually 17 when he left Hannibal then spent five years as a journeyman printer before tackling boat piloting. I think they looked at the illustrations in Life on the Mississippi and saw that the cub was represented as a "mere boy" so it was easier to skip over the printer years and cut to the chase and have him larnin' the river.
