Vic Fontaine was a holographic singer who was part of a program which simulated 1962 Las Vegas, Earth. He was a lounge singer who ran a nightclub in that city. He was modeled after entertainers such as Frank Sinatra and Dean Martin, and had a repertoire of swing-era songs that he performed with his band. Vic was designed by Felix to be fully interactive with the program's participants and was even aware of his holographic existence. Felix programmed Fontaine to be self-aware. Fontaine was so sophisticated that he was able to turn himself on and off. Fontaine was programmed to be highly perceptive of human nature and in that capacity proved to be a valuable mentor to many residents of DS9. Felix gave the program to his friend, Dr. Julian Bashir of Deep Space 9, who installed it in one of the station's holosuites at Quark's.
Because he was so advanced, the station crew began to think of Vic as a real person. He helped Odo with his attempts to win the love of Kira Nerys. Odo asked Vic for a little romantic advice in winning over Kira. Fontaine turned Odo into a tuxedo-clad piano player and invited a pair of beautiful holo-showgirls so that Odo could practice being at ease around women. Vic played matchmaker, told Kira about Odo's feelings, and arranged a date for them in his nightclub. Vic's advice and matchmaking paid off, and the two fell in love.
(DS9: "His Way")

After Ensign Nog lost his leg on AR-558, he struggled, both emotionally and physically, to cope with his disability, even though his new biosynthetic leg worked perfectly. Nog decided to take his medical leave in the Vic Fontaine holoprogram. At one point, Nog's sensitivity about his handicap erupted, and he punched Jake who had come to the lounge on a date prompting Vic to order Nog out of the club. Around that time, Nog had become Vic's personal accountant. Profits rose, but Vic realized that Nog was using the program to avoid reality, and prodded Nog to return to life aboard DS9. Vic abruptly ended the program, and Nog was unable to reactivate the program. When Vic reactivated himself, he was able to convince Nog to return to the real world. In exchange, Nog arranged for Vic's program to stay online continuously, enabling Vic to experience something close to real life.
(DS9: "It's Only a Paper Moon")

In 2375, a jack-in-the-box was activated in Vic's program. The unexpected plot development was part of the program originally designed by Felix. Vic was fired from his lounge as the mob took over his business. The crew of Deep Space 9 joined Vic and helped him regain his position. But it had to be done in a way that was period specific to the program. As such they devised a con game that got rid of the mobsters and restored the hologram to the way it was before.
(DS9: "Badda-Bing, Badda-Bang")

In 2376, Vic put on a special concert for the command crew of Deep Space 9 after the end of the Dominion War. It was the last time they were all together before many took new assignments after the war.
(DS9: "What You Leave Behind")