Cat Banzai Bill
From the Super Mario Wiki
Like normal Banzai Bills, Cat Banzai Bills are fired from Banzai Bill Cannons. However, unlike normal Banzai Bills, they will lock onto and follow the player, being very similar to King Bills in this sense. Also, unlike normal Banzai Bills, Cat Banzai Bills are colored white on their lower half, instead of being completely black. They will sometimes drop a Super Bell when defeated. They make their only appearance in The Bullet Bill Express.