I can't pull out my reference books to double
check myself (they're all packed and the only one
on top doesn't say), but I am sure that parts of
the Lion King (as well as Aladdin and Mulan also)
were done with cels.
I think that what you might have heard is that
The Little Mermaid was the last Disney animation
to be done *completely* by hand. (Although, I had
thought they did parts of the storm scene at
least with CG. . .) I have heard people say that
of Little Mermaid before.
If you're really dying to know for 100% certain,
ask me again in July when I unpack my books. ^_^
Many Sharp Smiles,