The Rugrats movie - Klasky/Csupo Inc

While the grown-ups are having fun at the Pickleses baby shower Tommy and the rest of the Rugrats gang search through all the baby presents looking for Tommy's new sister. Angelica says that babies are, 'a gift from Bob' but Bob isn't at the party and as the babies discover, neither is Tommy's sister. The hilarity continues when the babies go with Tommy to the hospital to meet his new sister, only to find out she is a boy and has been named baby Dil Pickles.
Baby Dil cries all the time and Tommy's friends don't like him, but Tommy has to take responsibilty for his little brother. So when the babies get lost in the forest and Dil is stolen by monkeys, it is Tommy's job to rescue him and steer the whole gang home.