Here is an example of an established actor being replaced very unexpectedly. It seems that General Hospital had difficulty with the role of Michael Corinthos, given that Dylan Cash, who had played Michael for six years, apparently expected to go on playing Michael after he emerged from his coma.

Producers had other ideas; they wanted Michael aged slightly, or SORAS'd (Soap Opera Rapid Aging Syndrome).

In 2009, they recast the role with Drew Garrett, who is five years older than Cash.

It turned out that the 20-year-old Garrett wasn't old enough, either, at least in looks. After winning over fans in the role, Garrett was shown the door just one week shy of his year's anniversary.

He was replaced by Chad Duell, who despite being just two years older than Garrett, looked more mature. The reason for the recast soon became obvious when Michael went to Pentonville Prison and was raped.  It was a heavy story arc, and certainly would have been much harder to take, or could not have been done, with such a juvenile as Garrett. 

Fans were unhappy at first, but Duell's strong acting soon won them over.  He's still with the show today.