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 taking out Mario.

The player is warned about the 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 that he/she isn't standing on any such blocks during such a violent destruction. On a side note, King Bills can also destroy blocks that Mario can break on his own.

Mario must also avoid going too high to avoid the King Bills. Since the whole level has clouds at the bottom that make Mario bounce very high, he occasionally must try to bounce under the stone 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 get under it 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 only 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.

There are a total of 7 King Bills in New Super Mario Bros. Wii, all of them appearing exclusively in the aforementioned level: 9-8.

Trivia

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