Feeling sorry for Ralph Wiggum,Marge invites him to play with Bart - who is hugely embarrassed until he learns that Ralph has access to his father's key-chain and can unlock any door in Springfield. After a night using the keys the boys end up in the disused jail,where they inadvertently activate the electric chair,causing problems for Mayor Quimby,who is visiting the jail next day, Disaster is averted,thanks to Lisa but Ralph's sinister imaginary friend,a leprechaun,has the last word.
—don @ minifie-1