Other mistake: In the opening credits Billy's name is misspelled as Bimmy. Bimmy and Jimmy, instead of Billy and Jimmy.
Factual error: In the Arcade, the map marker at the beginning of each stage is all wrong, being too far right - the US level starts somewhere off Nova Scotia, the Italian marker is in the Black Sea, etc. Home versions mostly fix it, but not quite; the Italian level in the Amiga version would be in France and the Egypt final stop is more like in Algeria.
Character mistake: In the arcade version, before entering the door with the three stones, Hiruko says "There is a secret hidden beneath HEAR, go."