MC Planter

Listen up, buttercup. This joke is playing on words. You see, "MC" is short for "Master of Ceremonies," a title often used by rappers. But it sounds like "emcee." So, the punchline, "MC Planter," is a pun. It sounds like "plant, sir!" because rappers are planting seeds, metaphorically, with their music, and also maybe literally. It's funny because it's unexpected and a little bit dumb, like you.