Here is a pencil frame from one of the Amazing Animals episodes. They were from the animated inserts for a live action kids wildlife program on the Disney Channel.
Here you can see the match lines in Red - So in clean up you had to make sure the lines matched those of the time machine he was sitting in (you couldn't just put him on a level below because his hands over lap the front of the windscreen).
The green line was to be clear that it is his coat. It just makes things a little clearer when passing on your work to an assistant or clean up artist. If you look closer you can see how the picture has been adjusted around the face area to make it better or animate right.