Now he looks at me, sort of funny, and says, "Do you know who I am?" I try to remember if I've seen him on TV or anything. "Are you the guy in those used-car commercials?"
Thank you for the context - it makes it much clearer.
It means the information struck him almost as though someone had hit him over the head with a hard object - suddenly and shockingly. It could be a brick or a ton of bricks - the meaning is the same.