Michael Sullivan was a character in Tom Paris' holodeck program called Fair Haven. He owned the local pub in the village of Fair Haven in 19th century Ireland. Most of the townspeople went to his pub, and he was a kind of town leader. In his original matrix, he was a simple man, with a wife named Frannie. Captain Kathryn Janeway visited his pub and became interested in him. She told him her name was Katie O'Clare . At the end of the evening, she was surprised when his wife appeared at the pub. The next day she altered his parameters, making him single and upgrading his intellectual abilities by giving him the education of a 19th century third-year student at Trinity College. Sullivan and Janeway went on to have a romantic affair. A storm caused damage to the program which Paris was going to repair but it would take several weeks and would't be able to retain the full program. Before Paris began his repairs, Janeway initialized Michael in the holo-lab and said good-bye (as before she had just deserted him with no note). She said that she may be returning to Fair Haven after several weeks and Michael invited her to stop by the pub if she did. She then made one final alteration whereby she would no longer be able to make any alter the subroutines of his program again.
Paris and Harry Kim pulled some pranks in a later holodeck visit, which caused the people of Fair Haven to become suspicious of them. Sullivan told Janeway that the townsfolk thought that she and her friends were evil spirits. When Paris and Kim transferred Sullivan to the holodeck to run a diagnostic on his program, Sullivan was surprisingly aware of his surroundings. Kim discovered that his perceptual filters were offline as were those of the other characters. After the townspeople captured Paris and Kim, Sullivan was transported off the holodeck using The Doctor's mobile emitter. Janeway explained to him about Voyager and they both returned to the holodeck. Sullivan calmed the townspeople down and convinced them that the Voyager crew meant no harm. The program was shut down for repairs, but not before the crew enjoyed one more night at Sullivan's pub. (VOY: "Fair Haven", "Spirit Folk")
In the Voyager novel Homecoming, Janeway visits Michael one last time just before she leaves Voyager upon her return home. He expresses jubilation when hearing that she finally made it home, and wishes her good luck, and she deactivates him for the last time.