Polterpup

Polterpuppy (at first known as ???) is a specific Polterpup character who appears throughout Luigi's Mansion: Dark Moon. Unlike normal Polterpups, he has a red collar instead of blue. His name, Polterpuppy, comes from a combination of "Polterpup" and "Puppy". E. Gadd surmises that Polterpuppy is lonely and is looking for someone to play with, but its attempts to do so accidentally cause trouble for Luigi.

History
Polterpuppy first appears in Gloomy Manor, where he is playing in the Mudroom Exterior. He finds a jewel underground and plays with it shortly before getting it stuck in a tree. At this point he leaves the Manor.

Later, Polterpuppy appears in Haunted Towers after Luigi finds the key in the pool, he runs up and takes it. He plays with it, similarly to what he did with the jewel, and throws it out the window. He chases after it, and is not seen until the next level, where Luigi hunts him down. Luigi finally catches him, but before he can store him in the Ghost Container, the pup managed to escape from the Poltergust 5000 and flees yet again.

Polterpuppy returns in the Old Clockworks, where he steals the second Clock Hand from a group of Greenies. Luigi has to chase after him yet again before finally catching him in the Poltergust 5000; unfortunately, the pup still manages to escape before he can be stored away.

Polterpuppy returns again in the Treacherous Mansion. Just before Luigi can go through the front door, Polterpuppy jumps out of the keyhole and knocks the key out of Luigi's hand. He flees to the basement, causing a long and paranormal chase through the odd rooms. This time, E. Gadd manages to have fixed the Ghost Container, meaning that the Polterpuppy can't escape.

Polterpuppy is finally released from the container in the end, after turning normal. Unfortunately for him, without anyone to play with, the pup is unhappy, but Luigi cheers him up, and after Polterpuppy has taken a picture with the other ghosts, Mario, and the Toad Assistants, Polterpuppy returns home as a new pet.

Also, whenever Luigi loses all of his health, if he has a Gold Bone with him, Polterpuppy will come up to him and lick him to health, even if the dog's trapped within the Ghost Container.

In-Game Description
??? - ''I haven't come up with a name for this mischievous and adorable Polterpup yet. He's caused us a whole mess of trouble, but I think the playful tyke just wants someone to take him in. I know! I'll call him Polterpuppy cuz he's so cute!''