I hope this makes sense, but in football games (NFL and NCAA), during the plays they will flash a merchandiser's logo on the field or they will show a big arrow and it will say something like "First and Goal". I'm sure you all have seen this at least once. Well, I know it's gotta be computer generated, but I am baffled as to how they make it look like the players are walking over the arrow or logo. It's really cool but I just can't figure it out.

Anyone know how they do this? I would Google it but I have no idea what to look up!

Andrea