The International Express Man
In Good Omens, this is the delivery and collection man who can always be relied upon. In appearance a somewhat defeated, rodent-like little man in late middle age, with a draggled moustache, dressed in a brown uniform overall and cap. From accent and verbal context he is the sort of "mustn't grumble" stoic working class British who, like Aziraphale is rooted very firmly in the 1950's.
However, other aspects of his trade are not so clear-cut. For one thing, he is charged with the supernatural delivery duty of finding the Four Riders and delivering the badges of office to them. (the Sword to War; the scales to Famine; the crown to Pollution; and the verbal invitation "Come and See" to Death ). He is clearly mortal and human, as the delivery to Death necessarily entails dying himself, and he is clearly aware of this as immediately prior to delivery, he writes a final love letter to his wife Ethel. This, and the fact that Good Omens is set within a world running on the Christian cosmology (which excludes the possibility of other pantheons and Gods) , rules out his being a Roundworld manifestation of the god Mercury (Fedecks).
Yet he delivers items of supernatural importance as if intervening time, space and oceans are of no consequence: first the sword to War, on a Greek island where she has provoked a brief bloody civil war; then the Scales to Famine, in a Des Moines burger lord; then the Crown to Pollution, as he lies on the verge of a formerly scenic and beautiful English river (identified as the Ick) then to England again to report to Death on behalf of the Three.
As Adam Young acts like a handful of grit in the machine and the Apocalypse winds down, the UPS man is reincarnated, as himself, to collect the badges of office again, from the tarmac of the American airforce base at Tadfield Common.
Is the delivery man more or less than he seems?