Bad Piggies is in the Angry Birds family, however it offers a different type of game with a unique perspective from the Piggies' point-of-view. It could have been a great game even without any link to Angry Birds.
Bad Piggies Free lite version has been released for both the iPhone and the iPad, and right now the iPad version Bad Piggies HD [$0.99 (HD) / Free (HD)] is actually on sale for 99¢, down from $2.99.Including the update that added new levels and content.
Along with the sale on Bad Piggies HD Rovio has reduced ALL of the other iPad-native versions of their games for Christmas. That's Angry Birds HD [$0.99 (HD) / Free (HD)], Angry Birds Seasons HD [$0.99 (HD) / Free (HD)], Angry Birds Rio HD [$0.99 (HD) / Free (HD)], Angry Birds Space HD [$0.99 (HD) / Free (HD)], Angry Birds Star Wars HD [$0.99 (HD) / Free (HD)], and Amazing Alex HD [$0.99 (HD)].
App Store Links: (The link will take you to your local version in your country)
Bad Piggies, $0.99 - UK version - 99p
Bad Piggies Free, Free
Bad Piggies HD, $0.99 (iPad Only)
Bad Piggies HD Free, Free (iPad Only)