In the original script (which was started 2-3 years before Simba's Pride was released) there were no Outlanders. It was only Zira (then known as Bianca), Kovu, and the three hyenas. In this script, Kovu was Scar's son. This was changed because if Zira was Scar's mate, then why would she team up with the hyenas, who killed Scar. They also had to change the fact of Kovu being Scar's son because that would be bordering on incest. (It would make Kovu and Kiara second cousins.)
Kathleen Turner was originally going to be the voice of Zira. Christian Slater was going to do the voice of Adult Kovu.