How to STOP MacBook from waking up when plugged in?

I have a MacBook for work in my home office, and I don't have enough outlets around my desk. So I unplugged it to use the outlet for something else. When I plugged it back in, I was startled to hear it play a notification chime. I turned on my monitor and saw that the computer had woken up from sleep, despite the fact that I did not touch it or do ANYTHING except plug in the power cord.

This is completely shocking and ridiculous behavior. I should not have to worry about my work computer waking up during non-work hours without any input from me whatsoever. It should turn on when I tell it to and ONLY when I tell it to. You'd think this is common sense, and yet I've scoured the settings and googled every combination of keywords, and I am still at a total loss as to how to disable this. Please help me.