I cannot stop smiling at this performance.
CLEARLY Nick Carter's appearance was a surprise. In her words:
"Comme une jeune fille tremblait"
It doesn't matter that she was already well known enough that she was Cœur de Pirate and NOT Béatrice Martin to the host. At the end of the day, she's a music fan, and that was her favorite Backstreet Boy.
She does start with a short cover of Bedouin Soundclash tune - "12:59 Lullaby". Recall that the vocalist of THAT band was also 1/2 of Armistice with Cœur de Pirate.