*Sighs*
alatar, alatar, alatar...are you being tongue in cheek regarding this topic? Be careful, or I may start quoting The Silmarillion regarding the balrogs flying "with winged speed".
Bombadil is not 'Eru's little joke'; he is, in fact, Tolkien's little joke. He is 'first' because he did indeed come far before the writing of LotR (Tom was that creepy little stuffed doll haunting the Tolkien's nursery). The ring does not affect him because he comes from outside of the story. He is a localized phenomena, a manifestation of something Tolkien felt important (the vanishing English countryside of his youth -- Bombadil is, for all intents and purposes, a version of the English Jack-in-the-Green), and Tolkien asked his publisher Unwin in a letter if he might include Bombadil for that reason, not because Tom had anything at all germane to do with the story.