Sneed's Feed and Seed
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
Sneed's Feed and Seed formerly Chuck's Feeduck and Seeduck