Because B-shells were too small.
Second Clown: I always perform in the big top.
So that he can sneak up on mice !
Po-po-po-po-po-po-poke-her-face
You Poke-r Face.
Because "B" shells would be too small!
Because B-shells are too small, and D-shells are too big.
Because "B" shells are to small and "D" shells are too big.