Brown also works extensively as a voice actor in animated TV series , notably portraying Lex Luthor on Superman : The Animated Series and Justice League\/Justice League Unlimited as well as Mr. Krabs on SpongeBob SquarePants . Brown also works extensively as a voice actor in animated TV series , notably portraying Lex Luthor on Superman : The Animated Series , Krypto the Superdog and Justice League\/Justice League Unlimited as well as his long-running-role as Mr. Krabs on SpongeBob SquarePants .