The Ghost Coach was the disguise of Rudy "Slippery Hands" Sable.
He was dressed in a ragged baseball coach uniform, and his face and skin were corpse-like.
He acted like a coach while scaring the little league players, telling a boy who missed a ball (after being scared by him) to drop and give him twenty push-ups.
Scooby-Doo (DC Comics)
Twenty-five years back, Sable robbed a bank in Smalltown. He was caught and sent to prison, but the loot was never found. When he got out of jail, he found the field where he buried the loot had been renovated and he couldn't easily find the hiding place. He got a job as a maintenance man to facilitate his search, and he dressed up as the Ghost Coach to scare people away from the Little League night games so that he could search without being disturbed.