When Chuck and Sarah open the door to their room, it is revealed to be cabin 50B. When Morgan zooms in on Chuck's ticket, it reads "Cabine 47B". That is actually the room number of Juan Diego Arnaldo. You can see the number behind him when Sarah is in his room.
In Castle, when Morgan addresses General Beckman, the first shot, from the front, shows him with his hands behind his back as he approaches the screen. The next shot, an immediate shot now from the rear, shows his hands crossed in front of him.
When Chuck throws the scooter through the window in the cafe, the stabilizer rollers are visible when it lands.
When Chuck is on the payphone with General Beckman, they are cut off and a recording says "Zwei Euro nachlegen, bitte," which means "Please insert two Euros." The Euro, however, is not legal tender in Switzerland. The phone should only accept Swiss Francs.
The B&W shot of the Paris train tracks that Morgan and Casey are looking at when trying to find Chuck and Sarah is actually of Moscow. The tracks lead to Kievskaya Train Station and also show the Stalin skyscraper at Smolenskaya Square.
The stock clip used to depict Lyon, France is actually of Faido, Switzerland.
Trains do not depart for Zurich from Montparnasse, but rather from Gare de l'Est.
Chuck and Sarah are traveling from Paris to Zurich in a train while Casey and Morgan figure out where they are, head to the airport, fly to France and catch them in Chuck and Sarah's train before they reach their destination. It would be simply impossible to do since Casey and Morgan's flight alone would take longer than Chuck and Sarah's train ride.
Though Juan Diego Arnaldo is supposed to be a Basque terrorist, the actor who plays him, Carlos Lacamara, uses his native Caribbean accent when he's speaking in Spanish.
When you buy train tickets, your name or alias is on the tickets. At 5:10, Chuck tells the steward of the dining car that they are the Charleses, nervously. Unless they purchased tickets under the name of Mr. and Mrs. Charles, they would not be on the registry for billing their meals.