As has been established a couple of times already round these parts, Hollywood has something of a problem with Extras. Despite the fact that thousands of films have been made in the past hundred years, and almost all of them hiring real life non-acting people to fill in the background, there doesn't seem to be a fool-proof method for making sure they're as tightly controlled as the main cast.
Given the precedent, you'd think directors would keep a reliable stock of so-called background artists that they know won't f*ck up, but necessity is the abusive mother of invention, and sometimes you just have to make the best of what you're given.
And often, what you're given is attention-seeking, unprofessional try-hards who ruin everything.
It's time, once again, to dip into the treasure trove marked Bad Extras to find the unprofessionals who took their opportunity for a little bit of limelight a little too enthusiastically and ended up doing the opposite of what a good Extra should do: blend in.