I thought it was an underestimated animal.
I was seeing this kind of drawing on Pinterest all day long, I really liked the style and wanted to make one of my own. But I wanted to do something a bit different of what was popular. Everyone was using powerful or safari style animals. So I tried to think of which animal was the opposite and I came up with the goldfish, because it has this reputation of being stupid.
Thinking differently is often thinking upside down.