Right, like in bughouse.
J@ wherever. That how harpies have always been used, and that's how they were invented (by me).
...
I'm not exactly sure what's happening, but dropped pieces can't capture (otherwise you'd just drop it on your opponent's king and gg 
).
So no, I believe that move was illegal. Provided it was a 'capture by dropping the Joker on the Spirit' move which I think is what happened.
So wait ... he dropped the Joker on the Spider after the Joker was captured by the Harpy?
I don't know what spiders are.
If the square was occupied by another piece, the harpy cannot drop a piece there.
How to spiders work?
How do jokers work?
How does that involve a harpy? Was the joker dropped by the harpy?
Sorry, I'm kind of confused. I have no experience with Infinite.
Yes it was dropped by the harpy, so we're deciding if that move is considered a spider move or harpy move. It has nothing to do with the board. 
legal
I think John said it was legal...
That was when he thought it was a spirit, not spider.
If a piece was dropped by a harpy, it cannot capture, otherwise you could just drop it on the king and win.
So if the piece (whatever it was) was dropped, it cannot be dropped on an occupied square.
NONONO John.
Basically A harpy dropped a piece the piece's move away from a joker, and we're deciding if the HARPY was moving (so the piece can't be captured), or if it was the PIECE, therefore the piece CAN be captured.
... yeesh. I'm really not sure.
I think that that move counts as a Spider move, because (S@ wherever), as it is in bughouse.
So I'm not clear on how the Spiders moves, but that move was not a harpy move. It would be a spider move.
I don't know if capturing is legal or not, I'm not familiar with these pieces.
But it was a Spider move.
Joker copies the move, so I can capture! JxS
What the? Wrong board.
There's 5 harpies tho! (but they are nerfed)