Punch Drunks (1934)

Moe discovers Curley's unknown boxing talent when he knocks out the Champ at a restaurant when Larry plays "Pop Goes the Weasal" on the violin. Moe becomes Curly's manager, and they win every fight, with the help of Larry. At the championship game, though, Larry's violin breaks. Curly is getting beat down bad when Larry makes his unexpected entrance and helps Curly prevail.