Samuel "Mayday" Malone is the main character of the series, and is the owner and bartender at Cheers for the majority of the series. He is one of only 3 characters that appeared in every episode.
Before his time at Cheers, Sam was a relief pitcher for the professional baseball team, the Boston Red Sox. He gained popularity, because he brought the Red Sox to the top of the table. Sam is a recovered alcoholic and a womanizer. He bought Cheers when he was still drinking and decided to hold onto the bar for sentimental reasons. His birthday is on October 17th.
Sam hires Diane Chambers in the first episode and eventually becomes romantically involved with her in the second season. After breaking up at the end of the second season, the two have a love-hate relationship from that point on. At the end of the fourth season Sam proposes to Diane. After many stressful times asking Diane to marry him, she finally agrees. At the end of the fifth season, when the two get to the altar, Sam tells Diane to go and fulfill her career as a writer instead of marrying him. Sam then sells the bar and leaves his friends, to sail around the world.
When he returns to the bar at the start of the sixth season he manages to get Rebecca Howe, the new bar manager, to hire him back as a bartender. He remained as a bartender until the final episode of the eighth season when he buys the bar back from the corporation he sold it to, for one dollar. Sam remains the owner of the bar for the rest of the series.
In Cheers's spin-off, Frasier, Malone appears in the Season 2 episode "The Show Where Sam Shows Up", where he is a self-declared sex addict who is engaged to Sheila, another sex addict (played by Tea Leoni), who admits to having sex with a lot of the patronage at Cheers. However, they break up when Sheila admits to having slept with Cliff.