In Chinese, there's an expression: 畫蛇添足 (literally: drawing a snake and adding feet to it). The phrase is used to describe a situation where you have completed the required task, but you do useless work on it anyway, resulting in you either missing a deadline (like the original fable), an unhappy customer, or both. I thought the closest equivalent to that was busywork, but when I was talking to a friend, he said I was using the word wrong, but he didn't know the right word either. Is there an English word or phrase that means the same thing?
Not a duplicate of this or the linked duplicate to that question either. Those questions deal with completing a task in a roundabout way. My question is about after they finish the task and do extra work anyway. Example: my company is tasked with building a computer, with a 1 month deadline. I finish building the computer within 3 weeks. My boss thinks I finished too early and wants me to (blank). I decide to come up with a way to make the computer talk. I either A: take too long and miss my deadline, B: irritate my client who just wants to type in peace, or both. (Ignore the unrealism of my example.)