Verses and concepts...

I've already written some verses to my story now. Also, here's the breakdown of it: The boy (or whatever) meets various animals who are doing what they do best (bird - flying etc) and he tells them that he can do better, then going on to tell an anecdote about a time in which he did something amazing. The animals don't act impressed because there is no logic to the stories and they are so ridiculous that they cannot possibly be true. He eventually realises that the last animal he talks to has walked off during his story, at which point he walks home. Then *SPOILER ALERT* we see his trophy collection, showing that he was actually telling the truth. So here are the verses I'm happy with so far and a page of sketches for the protagonist. As per, we're rhyming.

You call that swimming, fishy fish? That’s nothing, don’t you see?

One time I swam as deep as whales who all applauded me.

I met some mermaids, yes I did. I found Atlantis too.

And then the mayor proclaimed me king of all the deepest blue.

You call that running, furry feet? That’s nothing, what a bore.

One time I ran a race with cheetahs, antelope and more.

I ran around the Earth, I did, I even stopped for tea.

And for my speed I did receive not one medal, but three.

You call that flying, feathered friend? That’s nothing, not to me.

One time I flew out into space for aliens to see.

I flew beside an asteroid, and all cheered with delight.

And then I got a trophy for my brilliant skills of flight.

Now, why a fox? Well, foxes are often portraid in fiction as cunning, sneaky and sinister characters. This adds weight to the story. The reader will (hopefully) already have this in mind when they begin to read. This will make them believe that he is lying all the more, thus making the reveal at the end more poignant. Also the fox is native to the UK which I think is an added benefit for the child reader.
Also, here's a sketch showing the character in context a little.