Flag is an unused enemy in Mother 3, it was probably going to be like the enemies called Lamp and Doll from EarthBound Beginnings.

Its battle theme, like most unused enemies is "More Mischievous Blues".

His battle sound is Battle Sound 3 which falls under Code Numbers 445 for regular attack, 446 for Smaaaash! and 447 for Miss. Hacking the game is required to get him to use a regular attack as he has no attacks by default.