Complex sentence: When Graeme gives Tim and Bill a special'designer-dog' that they can enter the dog as a new breed in the Crufts Dog Show, they think that their dog is the only unusual dog there is.
Split into simpler sentences: When Graeme gives Tim and Bill a special'designer-dog' that they can enter the dog as a new breed in the Crufts Dog Show. They think that their dog is the only unusual dog there is.