The short films Stefano Pilati cooks up to introduce his men’s collections are turning into an Yves Saint Laurent tradition. Last season it was sexy talk abut zippers and close-ups of a moody Michael Pitt. For spring 2010, presented today, Pilati gave carte blanche to his friend, the writer and filmmaker Samuel Benchetrit, who dreamed up a tale about a little tramp, played by his son Jules, 11, who turns into a kind of cupid in a luxury suite at Paris’ Hotel Bristol. He’s dressed in various adult-sized pieces, including a YSL fedora, pinstriped blazer, perfecto jacket and wayfarers.

“I wanted to meld the spirit of a suit with sportswear,” said Pilati of the collection, which mixes boxy workwear pants with second-skin tank tops and beautifully worn-out double-breasted jackets so slim they look shrunk. At the post-show fête, held in the leafy courtyard of YSL’s headquarters, actresses Vahina Giocante, Elodie Bouchez and Anna Mouglalis—who, by the way, is Benchetrit’s main squeeze—were all buzzing around Keziah Jones, the Nigerian singer who mixed a suit with a T-shirt—just the way Pilati likes it.