Dream Celestia, fake phallus included, took only a second to fade out of existence. Long before any actual penetration happened to the poor stallion's exposed orifice. The same thing happened to Neil's muzzle, though the rest of his restraints remained. The fake version of herself, however, did not fade away. Instead, her form seemed to lose shape and shift until it was little more than a starry void in the vague shape of an Alicorn.