Crewman Daniels is an enlisted crewmember in Starfleet who serves on the USS Hood. His primary duties are janitorial, involving cleaning the miles of carpet on the ship (no thanks to Big Carpet) and cleaning the bridge during the night shift.
Daniels didn't exactly sign up for Starfleet to clean floors, but somebody's got to do it and at least he gets to see all sorts of new worlds in the process.
His paternal uncle also served as a crewman in Starfleet on the USS Enterprise-C.
Podcast Production Notes
Due to the re-use of Daniels in many janitorial and Big Carpet jokes by the Brothers Weems in both the Ship of the Week and What Would DeSoto Do segments, it would seem that Daniels might have transferred back and forth between starships on a regular basis to explain all of his appearances.