I am on my way to work (on the line 1) and just saw something rather extraordinary.
We were stopped at Nation when a plainclothes policeman hustled a young man in handcuffs up against the open doors. Then the policeman yelled down the car, "There's a woman who just had her cell phone stolen" -- and here he thrust the phone into the air -- "a woman with a small backpack who had her cell phone stolen" and asked if she could please come get it.
The police had obviously seen the pickpocket in action, while the woman wasn't even yet aware that her cell phone had been stolen!
It took everybody a minute to figure out what was going on (since the policeman were in plain clothes dressed like anyone going around Paris for the day), and the policeman with the suspect had to yell down the car a couple more times.
The woman's husband or partner finally came down to where the policeman was holding the suspect against the doors, which were still forced open. The man clearly wanted the policeman just to give him the phone, but the police insisted that he and his wife get off the train (as obviously they wanted them to press charges for theft). The guy and his wife finally got off, but they (non-French speakers, maybe Italian or Spanish or Portuguese) explained to the police that they were literally on their way to the airport and didn't have time to stop.
Meanwhile the RATP "driver" back in the command center (remember, this is the line 1, which has remote drivers) was asking the people holding the doors to stop holding up the train; it took them a while too to understand it was the police. And they admonished the officers for having blocked the doors without telling them. Finally we the passengers had to advise the RATP center that the police, suspect, and victims had moved away from the doors onto the platform, and that the remote center could close the doors and let us on our way.
All of this at 8:45 in the morning!!!