Here’s a basic rule for family contentment: Don’t play favorites with your kids. So when Japan’s Fast Company—the parent corporation of Uniqlo as well as the French labels Comptoir des Cotonniers (which sells sportswear basics) and Princesse Tam Tam (lingerie)—decided to throw the former a birthday bash, they threw the others into the mix, too. Uniqlo’s first Paris outpost opened a year ago, but lest its sibling brands feel left out, its first birthday party in Paris last night doubled as a 15th anniversary party for Comptoir, and a 25th for Princesse.

In a rambling hôtel particulier, each brand got its own section, decorated like a Parisian neighborhood. For Comptoir des Cotonniers, the main salon was restyled like a Montmartre apartment, where guests—like Becka Diamond, Style Bubble’s Susie Lau, and Street Peeper’s Phil Oh (pictured)—had their pictures taken and turned into real French postcards. (Stampswere provided to send them off.) Next door, Uniqlo held court in a space made up as a Paris loft in the 10th, with a line of carnival-style claw games to grab your prize (in this case, Uniqlo T-shirts, briefs, and badges tucked inside plastic canisters). But the best of all was in the hotel’s tapestry-lined library, where Princesse Tam Tam re-created a Saint-Germain Left Bank pied-à-terre. There, amid piles of PTT undies, artists sat patiently hand-painting names and other little messages for those who were willing to skip the dance floor—where André Saraiva, Irina Lazareanu, and Henry Holland were holding court—to make it to the head of the line.