There are not many series with a time-travelling turtle.
What do you think about Hedge? And please don't come now with
"They just wrote her into the series to finish it, because they had no idea for an ending"!
Because we only see her in one episode, we don't know much about her. And still I think, she's a interesting character.
The trail to and on the island was build by humans (obviously). Why did the creators used a turtle, that seemingly experience time in another way like normal animals? Maybe just to create some mystic touch to her.
When she has the power to call the Black Rabbit of Inlé, what was her purpose on earth? She called the earth "an island". Did she came from outer space? Or from another dimension? Maybe from the shadowland?
We have no answers to these questions. But we can conjecture here.
Hawkbit would say, that we're enlarging too much upon this, but luckily, this is
Darkling's Fiver's Honeycomb.
So let's come and join this theoretical discussion!
