Billy Christianson was Romy's love interest in the comedy Romy and Michele's High School Reunion.
Back in high school, Billy was the star quarterback and dating Christy. His popularity was so strong that he was crowned prom king. He's not particularly bright or deep, as he lets Christy tell him what to do.
In the present Billy is married with kids, but his life is such a disappointment that he's turned to the bottle for comfort and considers cheating on his wife as he believes she does the same.
Romy has always had a crush on Billy, though this was entirely superficial. During prom night she asked Sandy for a dance, who agreed despite dating Christy. Christy decided to dupe Romy into believing that Sandy had just dumped her for Romy, then she and Billy snuck away, leaving Romy alone and heartbroken.
Romy briefly considers trying to get back with Sandy, but upon seeing that he's turned into a drunken wreck, she realised he was never any good. Sandy propositioned Romy, who pretended to agree but left him waiting just as he'd left her all those years ago.
Christy and Billy were high school sweethearts. After high school they immediately eloped, which worked against both of them as Christy's career plans were discarded in favour of having kids and Billy was stuck in a dead-end job working for her father. By the time of their high-school reunion their marriage is more or less just for show as Billy suspects that she got pregnant to another man.