We rather enjoyed Kao the Kangaroo earlier this year, and Kao's new Halloween-themed DLC "Oh! Well" features five new Eternal Wells to conquer. These are mini levels that test your controller skills to the limit with moving and disappearing platforms, climbing challenges and lots of coins to collect. There are also five scary outfits to unlock by completing the new wells.
These new wells vary in design and look but are tougher than most in the main game, so should probably be left until last unless you're a Kao veteran. You can select both your unlocked Wells and the new DLC wells from any of the main Eternal Wells on any level.
A nice feature of Kao is that this is the third free DLC and that you can use the new outfits, and mix and match them while playing the new DLC wells or the main story campaign! Kudos to Tate Multimedia for supporting their game well after launch.