I recently had to change Airports in France from CDG to Orly when travelling to Barcelona for the Mobile World Congress. I had a Schengen Visa and on mentioning that I was on transit to Barcelona, they started demanding to see the invitation (Lucky I had it printed), whether I had some cash to take me Orly Airport, my credit card and a load of bullshit questioning by a guy who I could hardly hear because he was speaking very fast in a low voice behind the glass. I felt like asking him to speak up but felt like that wouldn't have ended well. After some moments he stamped the thing and threw it back.