Frank noticed his horse had a very long neck.
There's been a clerical error!
Someone has given him a giraffe for the race!
His ride craned over the horses.
It munched on overhanging trees.
The jockey made attempts to take back control.
He was shimmying up the beast's vast neck.
Swinging his arms wildly at the reins.

The only jockey anyone has ever heard of (excluding Jock(e)y Wilson, of course), Frankie Dettori, has been on my mind. I'm not sure how he got there, but there he is, hopping from thought to thought. I looked the man up on Wikipedia because I know nothing about him other than the fact that he's a jockey. It turns out his first name is Lanfranco. Additional facts include being in a plane crash and supporting Arsenal Football Club. None of this comes up in the poem. You're better off going to the page yourself if you'd like to know more. I think some of the information might be outdated.