Black Jack (TV) - episode 7 - 21 Nov, 2004

The white lion named Luna Luna, at the local zoo is sick. The lion's keeper begs Black Jack for help, but he refuses. It turns out the lion's illness is caused by a brain tumor which also caused his fur to turn white. After the operation, the now-gold Luna Luna is taken by Black Jack as his fee and released to the wild. (Source: Wikipedia)