Maggie Evans, Bride of Barnabas Collins (1967) and Maggie Evans, Bride of Barnabas Collins Revisited (1968)

Once upon a time, there was this crazy vampire named Barnabas who met a girl named Maggie who looked just like his dead girlfriend, so he did what any living dead psychopath would do:  he bit her, kidnapped her, then dressed her up in a close approximation of the clothes and hairstyle of his deceased paramour.  Flash forward a year, and the balance of Barnabas has shifted, slowly but surely, from emphasizing antihero to placing the emphasis on antihero.  For many people in the audience, they hadn't tuned in yet to the time when Barnabas was terrorizing Maggie on a daily basis.  Imagine, then, what a shock it was for audiences of the day when Maggie began experiencing flashbacks that forced the production team to recreate a storyline from more than a year before (mostly because those first-run episodes were filmed in black and white, and by the summer of 1968, Dark Shadows was broadcast in glorious color), a storyline where their vampire hero was violently loony tunes. 

Observe, then, the subtle differences in a powerful scene from #248 (June 7, 1967), recreated in #588 (September 25, 1968).  One of the most noticeable is Barnabas' fanging of Maggie in the 1968 recreation scene, which didn't occur in 1967.  Though Jonathan Frid was openly distasteful about any moment when Barnabas was required to bare his fangs, audiences loved it.

Aaaaaaand ... compare and contrast!