Lost had no shortage of powerful emotional moments, and many of these came in the form of long-awaited reunions between some of the show's most beloved characters. In a pivotal, life-threatening moment, season 4 reunited Desmond and Penny for the first time in years, and season 6 did the same for married couple Sun and Jin. However, there is one reunion that fans of the series never got to see (but likely did happen off-screen): Walt and Vincent.
In season 1 of ABC's Lost, Walt had a close friendship with his dog, Vincent. In the penultimate episode of season 1, Walt tearfully parted ways with Vincent when it was time for Walt, Michael, Sawyer, and Jin to leave the island on Michael's raft. Vincent chased the raft into the ocean as Walt waved goodbye. Later, the four encountered The Others, who kidnapped Walt. Michael spent most of season 2 trying to get Walt back. Finally, Michael and Walt were allowed to leave the island. For the remainder of the series, Walt didn't return to the island, though the character did make occasional guest appearances in seasons 3, 4, and 5.
In "The New Man In Charge", Lost's 12-minute epilogue that was released after Lost's series finale, Hurley and Ben find Walt as a patient in a mental hospital. The two convince Walt that the island is his true home. Walt agrees to go back with them to the island. Though Walt's return never happens on-screen, what happens next can be inferred.
Walt's dog, Vincent, still resides on the island as well after the Lost series finale. In fact, Vincent is one of only a few characters to come to the island in the series premiere, and remain there for the entirety of the series. In season 5, it was revealed that Vincent had been living with Rose and Bernard in a secluded cabin somewhere on the island. It seems likely that Walt and Vincent would have crossed paths at some point after Walt's return. Walt reuniting with the dog he hadn't seen since season 1 would have been a nice, touching moment, but would have been impossible to include during the lifetime of the series, due to the direction the series took Walt.
Audiences missing out on this reunion is a side-effect of the show's treatment of Walt, whose character played a key role in establishing Lost's island's mythos and mysteries in season 1. One of the show's earliest mysteries was Walt and what made him so special. Walt's importance to the show lessened after season 1, and before long, it appeared that the series had forgotten all about him.