Aaron Kelly was a Human male who served as an efficiency auditor for the Federation Auditor General in the 2270s.
In 2275, Kelly was part of a team that was sent to audit the efficiency of the USS Enterprise. While a member of that team, Kelly was a thorn in the side of ship's security, particularly security chief Pavel Chekov. This eventually culminated in Kelly illegally setting off an intruder alarm aboard the ship and Chekov hurting him as he responded to the alarm. Kelly was then thrown in the brig for his illegal action. Later, Kelly was nearly killed by an Orion spy and saved by Chekov, leading him to be extremely loyal to Chekov. (TOS novel: Death Count)