At the fish store, Alfred samples the caviar on offer using a metal spoon. Anyone with sufficient knowledge of caviar to be qualified to choose what to serve at a millionaires' dinner would know that caviar is only handled with a mother of pearl spoon, never metal, to avoid damaging the flavor of the roe.
When Penguin's henchman is administering the knockout gas to Alfred, he breathes in the gas himself, but isn't rendered unconscious.
Penguin kidnaps Alfred & brainwashes him. After doing so, he slips a fish hook into Alfred's coat pocket hoping it will reach the hands of Batman & Robin & lure them down to his pier so that he can trap them & kill them.
How exactly did the Penguin hope that the fish hook in Alfred's pocket would successfully fetch the dynamic duo?
He doesn't even know that Bruce Wayne & Dick Grayson are Batman & Robin; only that Alfred is Bruce Wayne's Butler.
At the millionaire's gathering at Wayne Manor, Bruce is careless about their secret identities. After learning of the fish hook, Bruce tells Dick they need to go to the Batcave to investigate, in front of a living room full of people. Normally, Batman takes great pains to be discreet about their secret identities.