turd in the punchbowl
vulgar slang Something or someone that spoils, ruins, or needlessly complicates a situation or circumstance; a disagreeable nuisance or source of irritation. For these greedy corporate executives, restrictions put in place by regulators to protect consumers are just turds in the punchbowl. Not to be the turd in the punchbowl, but I really think we should take this money we found to the police, instead of keeping it for ourselves.