I watched Count Duckula a number of times as a child. I recently wound up on the TV Tropes page while following a wiki-walk, and it made me remember the bare bones of one of the episodes. One of the conceits of the show is that Castle Duckula can teleport itself anywhere in the world, but always returns at dawn. In this episode, Duckula met a female (presumably a female duck, maybe even a vampire female duck) that he fell head-over-heels for. I remember he was trying to find something to give to her as a gift in the castle when it teleported back, and for some reason, he couldn't just go back, so she was lost forever, returning us to the status quo.
I'm certain someone more familiar with the series will know this one straight off, but I'm not having much luck looking through the episode summaries.