In Life, The Universe, And Everything, the 3rd book in the inaccurately named Hitchhiker Trilogy, Agrajag tells Arthur Dent about a place Arthur hasn't been to yet (meaning that it's logically impossible for Agrajag to kill Arthur; this doesn't stop Agrajag from trying); probably because the little bat's mouth was such a mess it sounded to Dent like Agrajag said Stavromula Beta (that's how it's spelled in LU&E). That's why Dent accidentally ends up there in Mostly Harmless.