Tebbis wanted to be a doctor. His patient number was "R-12". Due to his having a low TC, he was restricted to the Dinaali hospital ship's Level Red, where he befriended Dr. Voje and The Doctor. He believed music had healing properties. When a doctor was going to recycle a medical scanner, he took it and repaired it.
He was diagnosed with a chromoviral infection, and originally did not get the medicine needed. When The Doctor smuggled medicine in, his condition began improving, but he died of a secondary infection that spread rapidly. He did not receive treatment for the infection because he had already used up his allocation.
Enraged by the boy's death, The Doctor altered Chellick's blood factors by injecting him with Tebbis's antigens and the same infection he had, with the resulting effect that the Allocator believed Chellick to be Tebbis and refused to treat him. (VOY: "Critical Care")