Ghosts are obstacles in EarthBound
Ghosts reside in tunnels, warning any trespassers to turn back, forcing them to the entrance of the tunnel if they go too far into it. The only thing that will neutralize them is anything cheerful, such as light and music.
Ness must get a band called The Runaway Five from Twoson to help them get through the tunnel in their flashy musical bus to progress. The Ghosts will not be able to touch the bus, allowing the tourers to pass through without a hitch.
Their sprites are identical to Zombie Possessor overworld sprites in the same game. The discerning difference being Ghosts do not act as regular enemies, unlike the Zombie Possessors.