Frank Capra's "Meet Joe Doe" features a musical duet between Gary Cooper and Walter Brennan. Cooper plays a harmonica, but Brennan played what my father called a "sweet potato." I beleive you can also hear the sound of this "Sweet Potato" in the Sergio Leone westerns; especially "The Good, the Bad and the Ugly."
Since I no longer see them, I thought I would provide this entry from Encyclopædia Britannica;
Ocarina - (Italian: “little goose”),)
"globular flute, a late 19th-century musical development of traditional Italian carnival whistles of earthenware, often bird-shaped and sounding only one or two notes. It is an egg-shaped vessel of clay or metal or, as a toy, of plastic and is sounded on the flageolet, or fipple flute, principle."
If you want to purchase one for Christmas; here's a link from Amazon.com;