Arno is a Danish balloon crew chief employed by Terry Perry Barlow in the episode, "Of Human Bonding".
While Terry claims to have saved a balloon crew by opening a rip panel with his teeth, it was actually Arno who did so and he threatens to expose the story, claiming he has the dental damage to prove it.
Arno was quite bemused when Terry not only wanted to go ballooning in bad weather, but didn't think he needed a proper balloon crew but just "a teenager and a confused man?". The resulting argument, with both him and Terry threatening each other, caused him to bemoan how he missed the chance to be the first to solo balloon around the world to work for Terry, and that feels that he has failed his native Denmark. When Daria jokes he could be the first to solo around the world twice, Arno takes her seriously and immediately leaves to do so.