B. Bill Blaster

B. Bill Blasters (presumably short for "Bombshell Bill Blasters") are yellow versions of Bill Blasters that shoot Bombshell Bills, appearing in pairs in Paper Mario and Paper Mario: The Thousand-Year Door.

Paper Mario
In Paper Mario, B. Bill Blasters are a yellow-tinted black color and appear only in Bowser's Castle. They act just like the Bill Blasters found earlier at the Koopa Bros. Fortress, but are much stronger. They have very high defense and health, and their only true weakness is piercing attacks, though they have a slight weakness to shrinking. They shoot out Bombshell Bulls to attack for them, and skip every other turn. When a B. Bill Blaster is affected by any status condition, the Bombshell Bills it shoots are affected by the same status condition.

Paper Mario: The Thousand-Year Door
In Paper Mario: The Thousand-Year Door, B. Bill Blasters are now a very bright yellow and appear in the Palace of Shadow. They are now critically weak to many status effects, such as Tiny, Soft, Burn, and Freeze. Unlike in Paper Mario, they can shoot Bombshell Bills every turn, and can sometimes fire two Bombshell Bills when alone. Their Bombshell Bills can also be fired higher into the air occasionally, making them immune to ground-based moves like Mario's Hammer.