Espiègle translates to "mischievous" or "playful". It's a charming and less common adjective that adds a specific nuance to a description.
In the song, Jul uses it to describe his love interest's "sourire espiègle" (mischievous smile). This word paints a vivid picture of her personality, suggesting a playful and perhaps slightly teasing nature that captivated him, making it more engaging than a simple "beautiful smile".
Jul's "Toi Et Moi" is a sweet, straightforward love song about that instant connection you feel when you meet someone special. Our singer describes seeing this person and feeling an immediate pull, like they were "faits pour être ensemble" [made to be together].
He remembers seeing her a second time with all of Marseille in the background, noting her eyes were "aussi noirs que ma Twingo" [as black as my Twingo] – a funny, very Jul-esque detail! He was so smitten he could barely speak, probably seeming a bit "fou" [crazy] or "étrange" [strange]. But she didn't laugh; instead, she looked him in the eyes, took his hand, and kissed him. It's a simple, heartfelt story of love at first sight, emphasizing that feeling of knowing someone is the one.