When Michael Clayton spots Arthur Edens in the back alley, Arthur is carrying a bag of bread. In the beginning of the conversation, one loaf in the middle is missing its top, which apparently may have been eaten. In the following shots, the loaf is full.
When Clayton is in Arthur's loft and he picks up the red book from the coffee table, a folded slip of paper is sticking out from the bottom. A moment later, as he's flipping through the book, he almost doesn't see the paper because it's all the way inside.
When Michael and Marty are talking in Marty's home, the glass doors on the bookcase behind Marty change positions several times, probably to avoid reflecting the camera and crew in the glass.
When Clayton first gets the booklet from the print shop, it has a black plastic binding. Later, the binding changes to wire.
After Karen and Michael's final encounter, Karen looks off in Michael's direction as he walks away from her. In the next shot, she's looking straight ahead, 90 degrees to the right of her initial stance.
Arthur says "I am Shiva, The God of Death". Yama is the Hindu God of Death. Shiva is the destroyer or transformer.
Michael started with the firm in 1990, and has been there for 17 years. While speaking to Marty, he reflects on his state in life, and claims to be 45 years old. He was born in 1959, so he should be 47 or 48. He may be lying about his age.
Early in the film, during a drive in Manhattan, a tree is in vivid bloom, which occurs in spring. The rest of the film takes place around Christmas, with lit trees and decorations. In the rural New York scenes, the grass is dead and and actors' breath is clearly visible.
At 1:47:37 into the movie, Tilda Swindon, as she's looking at her self in the mirror, shakes her head back enough to see the light-colored/white piece under the red wig she's wearing at the top of her forehead and at the beginning of the wig line.
When Michael Clayton asks Marty for a loan, a crew member is reflected of a wooden door over Michael's left shoulder, moving back and forth. The actors are standing completely still.
Arthur locks the connecting door between his and Michael's room when Michael went to Wisconsin after Arthur stripped at the deposition, and Michael kicks in the door to get into Arthur's room. But Michael would have rented both rooms, and would have had a key to both rooms, and just could have gone in through the hallway door.