Green’s Dictionary of Slang

b.b.-brained adj.

(US) stupid.

1950		Van Nuys News (CA) 30 Jan. 11/1: Which of your BB-brained friends is running all over our lawn with cleats on.
1956		Blondie 15 Dec. [synd. cartoon strip] Mrs Woodley told me you called Herb a BB-brained baboon.
1969		letter in Times (San Mateo, CA) 30 July 34/2: How like our sensation loving and BB brained public.