Heathcliff and the Catillac Cats - Season 1 Episode 19 -

Heathcliff hears Iggy saying how wonderful it is to have a pet, and decides he should have a pet too. He tries out Spike and Mungo, but they do not make good pets at all. He frees a live lobster from the fish store which makes a great pet until the lobster begs to go home to the ocean and Heathcliff generously complies.