Kelso was a German Shepherd dog. He was the dog of Professor Frederick Marius. He had amber eyes.
Marius loved his dog and was talking to him a lot. When he had problems he would always go to Kelso to have a word with him. Even though Kelso never answered it, talking to Kelso helped Marius. (PROSE: One Man and His Dog)
When Marius wanted to work for the Bi-Al Foundation he had to leave Kelso behind. Since Marius loved Kelso so much he created K9 Mark I, a robot dog, which he was able to take to his new work place. (TV: The Invisible Enemy)