On Dallas, the character of Gary Ewing was originated by actor David Ackroyd.

However, when the decision was made to launch Knots Landing as a spinoff of Dallas, Gary was recast with Ted Shackelford, who played Gary for the entire 11 year run of Knots.

Does anybody know why David Ackroyd wasn't cast as Gary for the series?

Did he turn it down or was he committed to another series? Or did they just decide they wanted something different?

Funnily enough, David Ackroyd would appear on an episode of Knots later on in a different role.