King Bill

King Bills are a new sub-species of Bullet Bill that have so far only appeared in the final level of New Super Mario Bros. Wii; World 9-8. King Bills are invincible, being unable to be beaten through any maneuver, move, or item, and can only be avoided by bouncing above them with clouds and anticipating their deadly paths. Even a Star cannot neutralize a King Bill, but it can keep one from harming or killing Mario. Coins bundled together in the shape of giant bullets later will indicate where some of them will appear. Other times, Mario must avoid going to high to avoid them. Since the whole level has clouds at the bottom that make Mario bounce very high, he occasionally must try to bounce under unbreakable blocks to avoid going too high and not hit them. At the end of the level, a King Bill will chase Mario and he must outrun him and reach the end-level flagpole. Like Banzai Bills in Super Mario World, King Bill Blasters are not seen on screen.

It's very large in size, taking up nearly the entire screen, which makes it much larger than the previous biggest Bill, Banzai Bill. It is the biggest non-boss enemy of the game, being beaten out by Bowser's giant form after Kamek's spell in Bowser's Castle.

They show their teeth, like a Banzai Bill, but in a less menacing way. Additionally, their eyes are less menacing too. Interestingly enough, the King Bill's eye pupils actually follow Mario's movements.

On a side note, later in the level, the player is warned about certain incoming King Bills in the form of Coins that make a Bullet Bill shape design and several stone blocks that cannot be destroyed by anything except them. If Mario is standing on these stone blocks as the King Bill bursts through them, he will fall through onto one and be defeated. The player must make sure he not not standing on any such blocks during such a violent destruction. Rather, he can seek refuge on top of regular brick blocks.

There are a total of 7 King Bills in New Super Mario Bros. Wii.

Trivia

 * The Prima Player's Guide for New Super Mario Bros. Wii erroneously referred to the Banzai Bill as a King Bill.