The most significant change to Yoshi’s Island DS is the addition of interchangable babies, each with its own special capabilities. Baby Mario can run and hit Mario blocks, Peach can use her parasol to ride wind gusts, Donkey Kong can climb ropes and vines, and has a dash attack, Wario can move metal objects and attract coins with his magnet, and Bowser spits fireballs.
Throughout each level there are stork stations where you can swap out your current baby for any of the other babies that are part of your team. This allows for quite a bit of variation on the types of puzzles we've seen previously in Yoshi's Island.
None of these puzzles are too tricky, though. You might have to use Mario to hit some blocks so you can push a box to hold down a switch that turns on a fan for Princess Peach to use her parasol, but that's about as involved as it gets. Which is okay, because the emphasis here is still on great platforming, with just enough brainwork thrown in to keep you on your toes.