At my last job the HR guy installed this super annoying Slack bot that would spam everyone every week with a "happiness survey". I got so tired of it I eventually logged the requests my survey made and used curl to replay one with a happiness score of -100 (usually the value would be between 0 and 10). Response said "success".

Turned out the backend happily took that value and it skewed our average a lot and the next week I was laughing my ass off while HR was trying to figure out why everyone was suddenly so unhappy.