This week in children's apps features Clifford's BIG Birthday, a story about preparing a surprise party for the Big Red Dog. Also this week is Barbie: The Princess & Popstar, which tells the story of how Barbie meets another girl with whom she can swap identities.

Title: Clifford's BIG Birthday

Publisher: Scholastic

Release date: September 19, 2012

Price: $0.99

Background: Help Emily Elizabeth plan a surprise birthday for Clifford -- decorate his doghouse and then let the party begin.

Features: Customize the party including the cake, decorations and pick out a special present for Clifford, three interactive birthday-themed games, designed to build essential literacy skills using augmented reality.

Title: Barbie: The Princess & Popstar

Publisher: Random House Digital

Release date: September 6, 2012

Price: $3.99

Background: Barbie stars as Tori, the kindhearted princess of Meribella who would rather sing and dance than perform her royal duties. When her favorite pop star Keira visits the kingdom, the girls discover that they have much in common, including a magical secret that lets them look like one another. At first, swapping places seems like a great idea, until each girl realizes that the other’s life isn’t as easy as it seems.

Features: Karaoke sing-alongs, 15 stickers and three backgrounds to create a storybook scene, three slide puzzles, three reading modes.