Jero was a performer, a member of a pre-warp civilization in the Delta Quadrant. He worked for Kelis, who wrote their acting groups plays.

During the Voyager Eternals plays that they performed in 2376, he portrayed Tuvok, from the hot lands of Vulcan, where there is no laughter, and no tears. He felt that that was impossible, and that the audience would either think Tuvok was an unfeeling monster, or that he was a bad actor if he didn't cry when Harry Kim and B'Elanna Torres were lost.

When Kelis ran out of ideas, he gave Jero a scroll and told him to go into the mountains to deliver a message to Torres, and to not be afraid of a ship. He did, afraid of her clearly being an eternal, he ran back to the city. (VOY: "Muse")