I used to take the family dog trick or treating. He loved it. But he was the only dog out there amongst the kids--all dressed up in his costume. So, I've come across ghost dog biscuits. They're like little ghosts. What I can't figure out is the target market. Is it something cute to give fido. I assure you, they won't care if it looks like a ghost.
Alternatively, since so few dogs go trick or treating it makes little sense there. There are just damned few dogs who trick or treat.