This is one of Villager’s special attacks: the Lloid Rocket! You can either ride it or simply shoot it.
A new stage based on Find Mii II (3DS Mii Plaza game) will be appearing on Super Smash Bros. For Nintendo 3DS!
The turnips are part of Villager’s aerial attacks.
The number of turnips that appear in each attack are random. This comes from the fact that the turnip prices in the Animal Crossing games are different in each day.