Source: Radio Times
Source: CBS News
We have told you before how some casting choices that made history were a last-minute replacement. But in other cases, some roles weren't just almost played by different actors -- they were.
It has been said that casting is 90% of filming (or 80%, or 65% -- measurements differ, probably because of the metric system). We don't know if that's the reason why these failed to make a splash. Just look at them, and you tell us.
Source: Entertainment Weekly