This week’s free iOS charts once again showed a high rate of turnover, with new apps from Genera Interactive, Booyah and Breaktime Studios all making solid debuts on the iPhone chart. The week’s most interesting development came from Korean developer ISMAKER’s app SimSimi suddenly rocketing to prominence, moving up from the No. 169 spot to the No. 3 spot in three days. On the iPad, Apple’s new iTunes U app knocked Imangi’s Temple Run from the top spot.

This week’s top free iPhone Apps

SimSimi – Korean chat app SimSimi makes a left-field rise this week to kick off our charts in the No. 3 position. Developed by ISMAKER, the app bills itself as a “super advanced chatting robot.” Users of the app can engage in basic conversations with the SimSimi robot and can also teach the robot new words and phrases. The app was updated on Jan. 11.

Pet Town - Booyah’s newest game Pet Town makes a strong debut in the No. 6 spot on the free charts this week. Already at version 2.0 thanks to a Jan. 18 update, the game is  a citybuilding style title with real-world elements mixed in, similar to Booyah’s other game, My Town 2. Read our full review of the game here.

Sweet Shop – This week’s No. 10 app comes from San Francisco-based Breaktime Studios and its new game Sweet Shop. A business sim based around running a candy shop, players not only must manage a store, but must also cook up candy recipes, grow the ingredients and care for pets. The game monetizes through in-app purchases and also includes Game Center support.

Talking Princess - Genera Interactive lands on the charts in the No. 21 spot this weekend with Talking Princess, an interactive toy that closely resembles Outfit7’s offerings. The princess in the app will respond to touch input and repeat what users say.

Dream Train – Moving all the way down to the No. 30 spot we find Topgame Global’s Dream Train. Released on Jan. 18, the goal of the game is to take cute animals on a train trip. Players can customize the cars of the train, add furnishings and decorations. Advertised as free for a limited time, the game also monetizes through in-app purchases.

This week’s top free iPad apps

iTunes U – Apple’s new in-house app iTunes U leads the iPad charts this week in the No. 1 position. Boasting the world’s largest collection of free education content, the app gives users access to more than 500,000 free lectures, books and videos from educational institutions such as Stanford, Yale and the New York Public Library. The app is free but requires users to have iOS 5.0.

Order Up!! To Go – Chillingo’s latest game Order Up!! To Go makes a strong debut in the  No. 8 spot on the iPad charts this week. Developed by Irvine-based SuperVillain Studios, the game is a time management style game inspired by Cooking Mama. The game is free-to-play and monetizes through in-app purchases.

Hardy Pig HD – Moving to the No. 16 spot we find Hardy Pig HD, a fairly violent platformer that challenges players to prolong the life of a pig as it escapes from a slaughterhouse. The includes Game Center support and was last updated on Jan. 17. Hardy Pig HD is credited to Aleksey Volkov and iCreative.

LEGO App4+ – LEGO slides into our charts and claims the No. 22 spot with its latest latest app based on its line of toys, LEGO App4+. A simple game designed for children between the ages of four and seven, the app allows children to assemble a lego truck and collect bricks. The game was released on Jan. 16.

Triple Town – Finally closing out our charts we have Spry Fox’s mobile version of its critically-acclaimed Facebook Game Triple Town. Currently the No. 43 free iPad app, the game is an almost direct port of the Facebook version, but now includes the option to buy unlimited turns for a one-time in-app purchase of $3.99.