Greenie: A greenie is the first ghost that you will first incounter while you are in the Gloomy Manor. In the first mission in Gloomy Manor (A-1 Poltergust 5000) a Greenie will take the Strobulb and try to hide it in the Manor. Greenie's will appear a lot and try to get armed so be careful!
Slammer: They are the second ghost you can encounter in the Gloomy Manor and they will be a little harder to catch than the Greenie. Once they get mad they give you a "round of applause" but don't be fooled because that can make Luigi loose HP.
Hider: They are the third ghost you can encounter in the Gloomy Manor and will be slightly easier to catch than the Slammer. They can often be annoying because you will have to search for them when they are hiding. If you don't find them quick enough then they can start throwing stuff at you so have caution.
Poltergeist: They are the fourth ghost you encounter in the Gloomy Manor and act as a mini-boss and are the toughest ( not counting the boss ) ghost in Gloomy Manor with 100 hp. They turn invisible and throw books at Luigi using their telekinesis. Try flashing your Strobulb when the candles on the book turn blue.
Sneaker: You will first incounter this pink ghost in the Haunted Towers. They will try to turn invisible and try to scare you or damage you. Try and use the Dark-Light Device to see where they are. It might come in handy then you are trying to find one.