On the overnight train from Novgorod to Moscow.  When we got to the station, it turned out we had tickets for the prevous night.  David asked the lady attendant if it was possible to buy a new ticket (15 minutes before scheduled departure).  With limited Russian, it took awhile to catch on to the important part of the lengthy response, namely "do you need a receipt?"  Then it became instantly clear that the correct answer was "no," after which all problems disappeared.  We were a little nervous, since guidebooks talk about needing to secure the door to your compartment to avoid stangers breaking in during the night.  The attendant provided a "blockerator": a device that fits around the inside handle in such a way that it could not be turned from the outside.  Of course we had no problems.
 

On the Moscow River cruise boat.