The man knocking on the toilets door while Xavier is inside is the director of the movie.
The second instalment of a trilogy written and directed by Cédric Klapisch, which follows the journey of Xavier from student to family man. The first chapter is the movie "L'auberge espagnole", released in 2002, and the final chapter is "Casse-tête chinois", released in 2013.
The director never planned on bringing Judith Godrèche back for this sequel.
The Kookai store where Kassia works is at 155, Rue de Rennes in the 6th arrondissement of Paris.