Viking 1 is a satellite who was built by NASA and sent to Mars and like the real Viking 1 he became famous for becoming the first spacecraft to successfully land on Mars and perform his mission.
He is known to be proud of himself but also occasionally cranky especially after breaking down and realizing it was planned that way when his mission was over, remain on Mars for all eternity. The only company he has ever had is an ACAM Christmas angel named Tinselina who was put inside him by a kid at NASA and talks about nothing but Christmas.
At the near end of the film, he is seen saying goodbye to Tinselina as she has been invited to return to Earth by Toaster and the others.
Viking 1 was DeForest Kelley's only voice role in an animated film before he died of stomach cancer a year later.