My thought process when I read about Backpack Kid suing Epic over Fortnite using his dance included...
"Who the hell is Backpack Kid?"
"Is he an actual kid with a backpack or just a rapper with terrible naming abilities?"
"Was he a backpack bitten by a radioactive kid?"
"And I don't care anymore..."
All within the span of five seconds.
It's just money grubbers coming out of the woodwork. All these new lawsuits are reminding me of when Guitar Hero started getting sued by all those bands for stuff like "improper use of likenesses" or whatever. These people probably don't care or at least aren't aware, but when something blows up like Fortnite or Guitar Hero and they hear how much money is being made they just want a piece of the pie. This situation is different though since with Guitar Hero those people or at least their business people had to approve it and got paid to begin with.
That said, I don't think a person can own the rights to a dance with the current laws in the US. Yes, they may have created or popularized it, but it seems like it would sort of become "public domain" since anyone in the world can dance. It seems like they'll have a hard time truly having a case unless they can get some kind of copyright or whatever like the Carlton guy claims he is doing. Though he also says they used his likeness and that doesn't seem accurate to me. I'd guess most of these are just hoping that Epic will do an out of court settlement to avoid the headache of court. With "Backpack Kid", he is literally a kid so it's likely the parents with these thoughts. I'm not saying it's not a bit lame that Epic and other devs are just cashing in on these goofy dances instead of simply creating entirely original emotes, but I don't think it's illegal.