The new parents take Matilda out in Brooklyn. Plus: Katie, Lindsay and more

DESIGNING DUO

Justin Timberlake and pal Trace Ayala share a laugh Thursday at a party for their new clothing line, William Rast, at L.A.'s Kitson boutique. The name of the line reflects their collaboration: Timberlake's grandfather's first name was William; Ayala's grandpa's last name is Rast.