King Bill (New Super Mario Bros. Wii)
From the Super Mario Wiki
Ads keep the MarioWiki independent and free :)
New Super Mario Bros. Wii
King Bills only appear in World 9-3 of New Super Mario Bros. Wii. Unlike Bull's-Eye Bill, they only have a limited homing ability where they will track their target's vertical position and then continue forward once they reach that height. Their animation is very limited as well, always maintaining a horizontal position and never turning to point at their target.
The player can defeat it by simply jumping on its head, or by running into it with a Super Star. Also, a King Bill cannot be frozen by an ice ball; it will break the ice and release itself when the ice ball reaches it. Likewise, POW Blocks are useless against them.
King Bills are never seen being fired from a Banzai Bill Cannon.
Super Mario 3D World