Visible crew/equipment: In the beginning where Amanda Waller is talking in a restaurant. While the camera focuses on her towards the end of the scene, they move the camera right, facing towards her left side of her face. Watch the wine glass, you'll see the crew moving along with the camera.
Visible crew/equipment: When we see Floyd's past, he is on top of a building, lining up to assassinate someone and negotiating his fee on the phone. On the left middle, under a blanket, or something, there is another person on that roof when there shouldn't be.
Answer: Because he's already been into the liquid, it's how he became the Joker. He wanted Harley to be just like him.