Who will dance on the floor in the round
What does it even mean to "dance on the floor in the round"?
"In the round" is a phrase that identifies an architectural setup.
Usually applied to theaters, here the term establishes that seating surrounds the dance floor. When applied to theaters, the term means that audience seating surrounds the stage area.
The key idea here: Billie Jean is a star on the dance floor. All eyes are on her.
Billie Jean is not my lover
She's just a girl who claims that I am the one
But the kid is not my son
According to producer Quincy Jones, Michael based the song off of a real-life fan who had claimed he was the father of one—yep, just the one—of her twins.
Biographer J. Randy Taraborrelli explores this idea that Billie Jean was a young fan with mental problems, who claimed that Jackson fathered one of her twins.
The story passes from there into weirder territory, with suicide letters and more, but in interviews, Jackson never corroborated that story.
In fact, in 1996, Jackson himself offered a broader explanation of the 1982 song's origins:
There is a girl named Billie Jean, but it's not about that Billie Jean. Billie Jean is kinda anonymous. It represents a lot of girls who used to—they used to call them groupies in the '60s—they would hang around backstage doors and any band that would come to town they would have a relationship with. And I think I wrote this out of experience with my brothers when I was little. There were a lot of Billie Jeans out there. Every girl claimed that their son was related to my brothers. (Source)
And don't go around breaking young girls' hearts
In his life, Michael Jackson took that strong advice, never breaking too many hearts.
Over the years, Jackson has only been linked to a few people romantically. Around the time that he released Thriller, people speculated that he and Brooke Shields dated, though at his memorial service, Shields simple called theirs "the most natural and easiest of friendships" (source).
In the early '90s, Jackson married Lisa Marie Presley, the daughter of another king, Elvis Presley. The couple filed for divorce in 1996, and a few years later, Jackson married Debbie Rowe. She gave birth to two children before they also divorced in 1999.
Despite his two heterosexual marriages, rumors and speculation long swirled around Jackson's sexuality, with many believing that he was mostly asexual, and others suggesting he was gay.
Whatever the truth may have been—and Jackson was a very private person, despite his immense celebrity, so we may never know the whole truth—there is a certain irony to the subject matter of "Billie Jean." Michael Jackson was about as unlikely as any rock star ever to have fathered a child with a groupie.
For forty days and for forty nights
This is a common duration in the Bible, appearing in both the New Testament and the Old Testament as a standard amount of time for transformative changes.
If you've ever felt like you needed a change, the Judeo-Christian tradition certainly seems to suggest that you might want to take a good forty days and forty nights to take care of business.
You might be familiar with the Old Testament's flood story, in which God says, "I will cause it to rain upon the earth forty days and forty nights; and every living substance that I have made will I destroy from off the face of the earth" (Genesis 7:4).
Later, an even more familiar and important Biblical figure, Moses, hangs out with God on Mt Sinai for "forty days and forty nights" (Exodus 24:18) before emerging with the Ten Commandments and the Covenant Code.
Later still, Jesus spends the same "forty days" (Mark 1:13) in the desert, where he is tempted by the devil.
In each case, forty days (and forty nights, to get poetic on you) marks a transition, sometimes marked by challenges, as with the flood, the temptation of Christ, and Billie Jean accusing MJ of fathering her child.