Mouse on the Mayflower (1968)
The Mouse on the Mayflower is a 1968 animated Thanksgiving television special created by Rankin/Bass. It was the first official special under the Rankin/Bass moniker after changing its name from Videocraft the previous year. It debuted on NBC on November 23, 1968. The special is about a church mouse named Willum, who is discovered on the Mayflower. Tennessee Ernie Ford voices Willum and narrates.
More at Wikipedia.