Keenser was a Roylan male officer and engineer of the Republic Navy prior to and during the Clone Wars. In 22 BBY, Lieutenant Commander Keenser was in joint command of a mostly automated Republic outpost on Delta Vega, working with Montgomery Scott. He was Scott's only company for months before James T. Kirk arrived and he was recruited for the crew of the Enterprise.
Scott often belittled and berated Keenser, particularly regarding Keenser's tendency to climb up on things and the fact that his species required very little food. It was clear that they were fond of each other, however; Keenser, in particular, was saddened when Scott transported with Kirk to the Enterprise, although he later joined him.
By 19 BBY, Keenser had been promoted to Captain and was in command of the Venator class starship Bambula.