Vincent

Before The Crash

Walt's Yellow Labrador Retriever
Original owner was Brian Porter, Walt's adoptive father
Michael takes Vincent from Brian without asking after Susan dies and tells Walt that Brian gave him the dog. He does this both as an act to console his son and out of his contempt for Brian.
Presumably was in the luggage compartment of the aircraft

First seen by Jack after the crash wandering free in the forest.
Was brought back after the crash by Locke when he blew a whistle he carved.
When the monster noises are heard on the first night, Walt asks "Is that Vincent?"
Was placed in the care of Shannon by Walt before he left on the raft.
Since Walt is gone,and Michael,Michael is currantly back and Ana-Lucia is possibly dead,and Shannon is dead has become friends with Ana-Lucia or at least when she has food.
Changes owners a lot.
Was present right before Sun was attacked but didn't bark or defend her. It is possible that if he was still in the area he recognized Charlie and didn't see any reason for alarm.
Searching for Vincent is often used by the show's writers as motivation for the island residents to venture into the jungle.
- Walt's polar bear attack.
- Shannon's vision of Walt.
- Shannon's death.
- Locke and Boone's discovery of Claire after her escape from The Staff
Visited Shannon right before she was shot.
Vincent returns to the beach in S.O.S. just before Michael returns in the jungle with Jack and Kate
- Was seen with Sawyer, who was feeding him and petting him, at the end of S.O.S..
Vincent finds the Virgin Mary Statues in Sawyer's tent and brings one to Charlie in Three Minutes.
Acts very undoglike at times
- Did not defend Michael when Jin attacked him
- Was present when Charlie attacked Sun but neither defended her nor even barked.
Has been abandoned on the island by Michael and Walt.

Possibly related to one of the mysteries on the Island. Evidence: Season 1 Episode 2 (Pilot part 2) - When Boone, Shannon, Charlie, Sawyer, Kate and Sayid move out for the hill to receive a signal with the transceiver, they are watched by Vincent (the camera is said to point on Vincent hiding in high grass, although very little seems to support this claim).
Possible is the "eyes" of the others. People speculate that he is somehow a spy planted in the group by the others.
Javier Grillo-Marxuach called Vincent "the dog of doom", perhaps signifying that his appearances are bad omens.
Possible connection to the "spirit dog" that Locke's mother claimed appeared just before his sister's death?
Possibly the reason that Shannon is able to see Walt's whispering figure in the jungle. Walt has a spiritual connection to Vincent, which is transfered to Shannon when she begins taking care of him after Walt's disappearence.
May have abandonement issues due to having so many different owners in such a short span of time.
Along with the coming of rain, maybe be a harbinger of impending misfortune.