Keenser was the protagonist of the Star Trek #14 - Keesner of IDW Publishing's Star Trek: Ongoing, which identifies Keenser as a Roylan from the planet of Royla. Keenser was often ridiculed by his classmates because he was taller than all the others of his species.
In 2230, after first contact with his people was made by the United Federation of Planets Starfleet ship U.S.S. Kelvin. Keenser demonstrated his engineering skills to the Kelvin's first officer and James T. Kirk's father, Lt. Cmdr. George Kirk, and security officer Lt. K'Bentayr by giving them a complete diagnostic and pinpointing their problem. Keenser was allowed to leave with the Kelvin's away team to join Starfleet.
Keenser graduated from Starfleet Academy in 2233, becoming the first Roylan to have left Royla and join Starfleet, dedicating his service to the fallen George Kirk. Keenser is identified as having the rank of Lieutenant. His service on Delta Vega preceded Scott's, having outlasted all the other personnel formerly employed there.
In "The Tholian Webs, Part 1", Keenser was rendered unconscious, after Scott went mad and tried to take over the ship. In "The Tholian Webs, Part 2" Keenser saves the vessel by knocking out Scotty and devising a way to cause a plasma burst to free the ship. Captain Kirk subsequently noted, in a captain's log entry, that he wished to commend Keenser. They thereafter had a drink together in the ship's lounge and, although Kirk tried to make conversation, Keenser was extremely quiet, as usual.
In a parallel universe depicted in "Parallel Lives, Part 1", a female equivalent of Keenser, named "Keensera", is shown serving as a lieutenant aboard the Enterprise of that reality. Marjorie "Scotty" Scott, the ship's chief engineer, mentions she initially suspected Keensera of causing the entanglement by messing about with the Enterprise's functions in the ship's systems.
Star Trek Into Darkness
Star Trek Beyond
Star Trek (2013)
Delta Vega: Meltdown on the Ice Planet (β) - Esurance Flash Game