Miles was a scientist/doctor who visited remote parts of the world to help people who did not have access to medical help. He did not have much of a love life, as he felt that no woman would put up with all of the travel he had to go through, until he met someone who not only put up with travel but did quite a bit of it herself - a doctor/botanist named Stella; however, two or three years after their son Arnold was born, they had to fly one more mission, and they haven't been heard from since.
Whether Arnold rescues them is left up to the audience since a planned movie that would show Arnold searching for his parents in a jungle was cancelled after Craig Bartlett left Nickelodeon.
Fittingly, the role of Miles was read by the franchise creator, Craig Bartlett.
es:Miles (Oye Arnold!)