The joke is that it is Sneed's Feed and Seed which rhymes but the sign says it was 'formerly
Chuck's. Therefore, it is funny because if the store used to be
Chuck's then it must have been called
Chuck's Feeduck and Seeduck in order to maintain the rhyme scheme, but hilariously Feeduck and Seeduck arent actual words in the English language which is funny. Wow the Simpsons is such a great show how did the writers get away with this one