The Casey Bat is a weapon in EarthBound. It is obtained after defeating Master Barf in Deep Darkness, and can be equipped by Ness. The Casey Bat is named after the baseball poem, "Casey at the Bat; A Ballad of the Republic Sung in the Year 1888". The bat's stats are heavily linked to the context of this poem.
It increases Ness' Offense stat by 125, making it the strongest overall of his weapons, but will only hit 25% of the time under normal circumstances. However, its accuracy and the chance of it scoring SMAAAASH!! hits increases as Ness' party members are knocked out, and while fighting opponents much stronger than the party. In addition, if used directly from the inventory, its accuracy is increased.
While appearing largely useless, the Casey Bat is useful in getting Instant Wins while not necessarily being at the required level. This proves helpful in instances such as retrieving items with a 1/128 chance of appearing (e.g. Starman Super and the Sword of Kings).