Wallzie

A Wallzie is a homerun down the first or third baseline that passes through the outfield wall, rather than passing over it. This is often considered to be a glitch, although RBI players generally recognize Wallzies as legitimate homeruns when they occur in competition.

The Wallzie occurs in both the Arcade and NES versions of RBI, and it is believed to be the only way that a pitcher homerun can occur.