RATP is the state-owned public transport operator. RATP stands for Regie Autonome des Transports Parisiens (or in English "Autonomous Operator of Parisian Transports"). They run most of the public transport system (Metro, Tram, Bus and some of the RER) in Paris.
RATP reserved several Twitter accounts for tweeting updates for the public transport network. They launched several accounts recently (@Ligne1_RATP, @Ligne4_RATP, @Ligne12_RATP, @Ligne13_RATP). RATP reserved the remaining accounts however, someone managed to divert the unused accounts and has been using them to send parodies of the RATP transport announcements.
The RATP, showing their good natured side, have collected the parodies and put them on a tumblr account called "RATP Hall of Fake". The fake Twitter accounts have now been suspended.
Here are some of the better ones.
Ligne3_RATP: @Ligne2_RATP Hi Line 2, I'm Line 3. Let's meet at Villers or Pere Lachaise (metro stations)
Ligne8_RATP: Good news, I have finished eating - Traffic will resume
Ligne11_RATP: Hey You, the big guy with the brown hair who jumped the turnstile at Republique
(metro station) ....I see you!
Ligne14_RATP: Is there a driver on the Metro?
Ligne14_RATP: Attention, this metro is not taking any more passengers! (I have to be lighter for the race with line 7).
Ligne14_RATP: I have to pick up a pizza from Olympiades (metro station). Therefore I will not make any stops from Saint-Lazare (metro station) to keep them warm. Sorry