In contemporary slang, the phrase "I have a surprise for you, it's poop" is often used humorously to indicate that someone has a surprising or unexpected disappointment or underwhelming news to share. It's a lighthearted way to playfully lower someone's expectations, with the humorous twist that the "surprise" is something mundane or unpleasant, like finding out the surprise is simply "poop." This phrase is generally used in casual, informal contexts and should be taken in a light-hearted spirit.