S10E08 Homer Simpson in: 'Kidney Trouble'
When Grampa needs a kidney transplant Homer is the obvious donor but he chickens out and runs away to sea. On board ship his fellow passengers are disgusted by his cowardice and throw him overboard. Drifting to the shore he sees a father and son bond over building a sand-castle and knows what he must do. The transplant is a success - though its circumstances are unusual,to say the least.