To quote from wiki - “Wowbagger is an alien who became immortal due to an accident with an irrational particle accelerator, a pair of rubber bands and a liquid lunch, so therefore does not know how to handle being immortal. This is in contrast to the rest of the immortal beings in the universe, who are, in his opinion, "a bunch of serene bastards." He eventually comes up with a plan to keep himself busy: he will insult every living being in the universe - in alphabetical order. He appears in the third book, Life, the Universe and Everything, while insulting Arthur Dent with the phrase: "You're a jerk, Dent; a complete asshole" “
I love Douglas Adams's work and I have been fascinated by immortality. Logical choice given the two.