In season 4 when Charlie visits Hurley at the mental institute, 2 very interesting things happen. First, another patient at the institute comes up to Hurley stating that a man is staring at Hurley, and when the patient points to the man he is pointing at Charlie. If Charlie truly is dead, how can this man see that he is staring at Hurley?
Secondly, Charlie keeps insisting that he is "Here" at the institute with Hurley, but that he is ALSO Dead. When Hurley freaks out that he is dead and cant be there, Charlie keeps insisting that he is in fact there. Is it possible that Charlie in one time loop truly is present and alive in L.A. while the Charlie we knew is dead in the time loop from Seasons 1-5?
Is this Charlie that we and Hugo assume is an apparition actually a living Charlie?
On a side note, his appearance is much different than any time we see him on, or before the island (in my opinion dressed a rock star who has been reaping royalties from a greatest hits album)