I started by sketching out a core cast of characters and learning about the underwater creatures that would be a part of the series. Little Nemo looks a bit like Splash, the first character I designed. Little Nemo was released a few years after we began selling episode one :p
After creating the initial cast of characters and rendering a vision for the series, I was able to add to the development effort. Together, we brought the first episode to market within a year. Two more episodes followed soon after.
Kingdom Under the Sea was a success for while, but not a hit. To this day, it is available for sale at various retailers in many languages. I have the Korean version - that's my favorite.