We too were approached by a street artist, not in Place du Tetre, but in one of the many side streets. He was wanting to draw our portrait, and when I asked to see a sample of his work he did the sell, promising that if we didn't like our portrait we didn't have to pay.
So, we settled in at a sidewalk cafe, with tea and coffee and chatted while he drew. It is quite an unnerving experience having someone stare at you so intently. The banter flowed freely, we talked about travel, the history of Montmartre and art. It was fun. We also talked a lot about the beautiful young woman (me) and the man with a face filled with character (Frank). It was all part of the sales ploy, but still charming. The sketch looked nothing like us, but as a study of a couple al la Parisienne it was cute, and yes we bought it.