A little green blobby planet thing, nicknamed the “Cosmic Cutie”, with no eyes, a tongue and two sticky-out arms, was used on the U.S. editions of the Hitch Hiker’s Guide To The Galaxy series of books because of worries that American people might not realise that a series of books with completely different names was actually a ‘trilogy’.
Douglas was one of many people who hated the little thing, and managed to ensure that it is not going to appear on any new editions of any of his books.
The only tangible relevance that the green thing has with the story itself is an appearance in the BBC TV series, in the section of the Book narrative discussing the population of the Universe. When it is said that the population must be “as near to nothing as makes no odds”, a string of noughts appears (0.000000000…), one of which, momentarily, turns into the Cosmic Cutie, waves, and disappears.