I think that the balloon was a balloon from their honeymoon, the teddy bear was her childhood teddy bear, the flower was planted on his grave, the necklace was hers, the bow was just a pretty thing, and etc. For a category i would put it under "perfected".
At first i thought he was alive and she was just ignoring him, but when i saw he kept getting less substantial with every gift I began to wonder, and when i saw to tombstone that made me sure that they were lovers and he died. After that i realized that she had brought him back to Earth as a ghost because of her grieving for him. So he tries to make her happy again by bringing her gifts. All in all, IT WAS REALLY SAD. :'(
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