I read this book about 30-35 years ago when I was 9-12, it was illustrated with cartoony yet cool pictures in color. I have no memory of the cover, I think it may have been paperback. It is the story of some animal friends, one of whom discovers a walled/gated garden that is completely overgrown. It has a fountain that doesn’t work, and while it once was beautiful, is basically unrecognizable because it was abandoned. I can’t remember what animal the main character was, but I think it was a kangaroo or a giraffe and for some reason I think the name was Geoffrey or Jeffrey. Not sure though.
He works in secret to completely restore the garden and fountain, while keeping the exterior appearing unchanged. His friend misses him and worries that they are growing distant since the main character is spending so much time working in the garden.
At the end, there is a birthday party and the protagonist rigs the hedges of the garden in sections and hands a string to their friend having the birthday to pull, which they do, revealing the transformed garden and splashing fountain to the astonishment and delight of all. I think there is then a celebration with a very special cake, perhaps orange chiffon, perhaps I am making that up.
I read this book over and over and now want to read it to my kids but can’t remember title or author and none of my searches are working. Hope you can help!