Yoshi's Island DS

Yoshi's Island DS was future Bowser and Kamek's failed plan to harness the power of seven babies to conquer the universe.

History
One night, Kamek and his Toadies stole every baby from all around the world. The Stork intervened in the attack and released the infant Mario and Princess Peach from their grasp.

Because the castle hung above Yoshi's Island, the babies landed near a Yoshi. The Yoshi clan decides to once again save Baby Luigi and, in turn, every baby in the world. The Stork joins the clan for easier transport between each of the babies.

Kamek does eventually find out that the babies are being transported by the Yoshis again and uses his enhancive magic on enemies again, turning them into bosses to stop the clan.

While Peach is kidnapped by an Ukiki, Baby DK lands on the Yoshi's lap. His help traversing through vines is greatly appreciated, so he joins the team. Peach is rescued after a short while.

After finishing up on Bessie Bass's Battleship, a flash flood washes everyone apart. Yoshi, alone in a cave, hears a shrill cry which turns out to be Wario. The Yoshi decides to take him along. After making it out of the cave, Yoshi regroups with the rest of the babies and the Stork. After finishing up at Castle of Priscilla the Peckish, Wario notices some Bandits carrying some coins and leaves the group to go after them.

Baby Bowser was also kidnapped from his Kamek. It turns out that the Kamek that's been kidnapping all these babies is from the future, and they've been collecting all these babies to find the seven star children; children possessing a power great enough to conquer the universe, which future Bowser intends to do. Baby Bowser scoffs at the idea he'll still try and take over the universe even when he turns into an old geezer. In anger, future Bowser pushes his infant self down his castle that's hanging above Yoshi's Island.

Baby Bowser lands on Yoshi and decides to hang out with the other babies for a while. After finishing up at the Castle of Big Guy the Stilted, Baby Bowser attempts to follow the future Kamek, but falls off and vanishes from the team.

The babies arrive at Bowser's Castle where they meet up with Wario and Baby Bowser arguing with eachother. After not finding the future Kamek and Bowser, Baby Bowser then wants the babies to leave and fights them for not doing that. After fighting Baby Bowser, future Bowser crashes from the ceiling to fight Yoshi. After that wasn't enough, Kamek then grows Bowser to a fairly big size. All of the Yoshi clan bands together in this instance and defeat Bowser.

Future Kamek swears that the Yoshis will pay before retreating with an unconscious Bowser in tow. Yoshi continues further and finds the missing babies, including Baby Luigi. Quickly, all of the storks retrieve the babies before Bowser's Castle crumbles and they are all returned back to their homes.

Wario releases himself from his Stork's grip and takes a big dip in the washed-up treasure from Bowser. Baby Bowser then lands on Wario and the two argue over the treasure.

It turns out that the seven star children were the babies that the Yoshis were carrying, including Luigi. The seventh, our Yoshi, then gets born.

Timeline

 * Takes place some time after the previous three titles, as the Baby Mario Bros. are kidnapped from their home.
 * Baby Yoshi is born at the end.